Influence of Cooling Rate on Microsegregation Behavior of … · 2016-04-20 · Compositional...

Research ArticleInfluence of Cooling Rate on MicrosegregationBehavior of Magnesium Alloys

Md Imran Khan1 Ahmad O Mostafa1 Mohammad Aljarrah2

Elhachmi Essadiqi3 and Mamoun Medraj1

1 Mechanical and Industrial Engineering Department Concordia University 1455 de Maisonneuve Boulevard WestMontreal QC Canada H3G 1M8

2 Industrial Engineering Department The Hashemite University PO Box 330127 Zarqa 13115 Jordan3 Renewable Energy ampAdvancedMaterials Research Lab International University of Rabat Technopolis 11 100 Sala el Jadida Morocco

Correspondence should be addressed to Mamoun Medraj mmedrajencsconcordiaca

Received 28 November 2013 Revised 7 January 2014 Accepted 10 January 2014 Published 3 March 2014

Academic Editor Necmettin Maraslı

Copyright copy 2014 Md Imran Khan et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

The effect of cooling rate on microstructure and microsegregation of three commercially important magnesium alloys wasinvestigated usingWedge (V-shaped) castings of AZ91D AM60B and AE44 alloysThermocouples were distributed tomeasure thecooling rate at six different locations of thewedge casts Solute redistribution profileswere drawnbased on the chemical compositionanalysis obtained by EDSWDS analysis Microstructural and morphological features such as dendrite arm spacing and secondaryphase particle size were analyzed using both optical and scanning electron microscopes Dendritic arm spacing and secondaryphase particle size showed an increasing trend with decreasing cooling rate for the three alloys Area percentage of secondaryphase particles decreased with decreasing cooling rate for AE44 alloy The trend was different for AZ91D and AM60B alloys forboth alloys area percentage of 120573-Mg

17Al12increased with decreasing cooling rate up to location 4 and then decreased slightly The

tendency for microsegregation was more severe at slower cooling rates possibly due to prolonged back diffusion At slower coolingrate the minimum concentration of aluminum at the dendritic core was lower compared to faster cooled locationsThe segregationdeviation parameter and the partition coefficient were calculated from the experimentally obtained data

1 Introduction

Environmental concernwas the keymotivating factor behinddevelopment of Mg alloys Better aerodynamic design ofvehicles or engines with improved combustion efficiency canlessen fuel consumption but weight reduction seems to bethe most effective way to achieve a substantial fuel saving[1 2] Magnesium with density of 174 gcm3 is the lightestof all the engineering structural metals [3] Mg-based alloyshave an excellent combination of properties which justifiestheir usage in transportation applications These propertiesinclude excellent strength-to-weight ratio good fatigue andimpact strengths and relatively large thermal and electricalconductivities [4]

All commercial magnesium alloys are multicomponentand form a variety of phases during solidification andsubsequent processing stages High-pressure die casting andgravity casting particularly sand and permanent mold cast-ing are the common casting processes used to produce Mgalloy components Other pertinent production technologiesinclude squeeze casting thixocasting and thixomolding[5] The wide range of operational conditions existing infoundry and casting processes generates as a direct conse-quence a diversity of solidification microstructures Becausemicrostructure determines the final properties of the mate-rial proper understanding of the microstructure formationmechanisms is extremely important Mechanical propertiesdepend on the microstructural arrangement defined during

Hindawi Publishing CorporationJournal of MaterialsVolume 2014 Article ID 657647 18 pageshttpdxdoiorg1011552014657647

2 Journal of Materials

solidification such as the amount and distribution of eutec-tic phases grain size dendrite spacing and porosity [6]Segregation or redistribution of solutes during solidificationis closely linked to dendrite arm spacing interdendriticporosity and the amount and distribution of eutectic phases

Themechanism ofmicrosegregation during solidificationof aluminum alloys has received considerable attention butmicrosegregation during solidification of magnesium alloyshas not been systematically studied To understand theinfluence of cooling rate on microsegregation of magnesiumalloys this work aims to carry out an experimental investiga-tion using wedge cast samples of AZ91D AM60B and AE44alloys By applying thewedge casting solidification techniqueit is possible to produce a range of cooling rates in one casting

2 Literature Data

Very few experimental works [7ndash10] regarding the microseg-regation analysis of magnesium alloys were found in theliterature In contrary several studies [11ndash20] were carriedout to investigate the solidification behavior of magnesium-based alloys Although the prime focus of these studieswas not on microsegregation analysis valuable informationregarding elemental composition at different cooling ratesand conditions could be obtained from them Mirkovicand Schmid-Fetzer [8 9] studied the microsegregation ofAZ31 and AM50 alloys applying directional solidificationtechnique They reported that the segregation behavior ofmanganese is opposite compared to both aluminum andzinc This can be explained by understanding the ternaryMg-Al-Mn system where the Mn forms a peritectic systemPeritectic systems are known to show reversed segregationZhang et al [10] studied the microsegregation in direc-tionally solidified Mg-4Al binary alloy They determinedmicrosegregation in specimens directionally solidified withcooling rates ranging from 006 to 08 Ks They reportedthat the concentration profile of Al at high growth rate orhigher cooling rate is closer to the Scheil model Zheng etal [7] investigated the microsegregation pattern of Mg-4Al-4Ca alloy under different growth rates using the directionalsolidification techniqueThey suggested that the Scheilmodelcan be used in microstructure simulation of this alloy asthe microsegregation of the alloying elements (Al and Ca)predicted by this model agreed reasonably well with theEPMAmeasurements

Wei and Warren [21] carried out microstructural char-acterization of several magnesium alloys in the AM seriesin as-cast condition They performed quantitative analysis ofthe Al segregation in the die cast alloys by examining thinfoil specimens in the TEM Compositional measurementsacross an 120572-Mg grain in AM50A at intervals of 180 nmwere performed using X-ray energy dispersive spectrometry(EDS) in the TEM along a straight line They found that theAl composition in the interior ofMg grain was approximately15 wt which increased to 30 wt in the area adjacent tothe grain boundaries They repeated the same procedure fora thin foil sample of die cast AM60A at intervals of 600 nmThe Al content varied from 2wt in the grain interior toapproximately 4wt in the Al-rich grain boundary region

The width of the high Al region was about 2-3mmThey alsoreported that owing to the low Al content no 120573-Al

12Mg17

formed in AM20 but there was intergranular Al segregationBarbagallo et al [19] determined the variation of the

alloying element contents through the grain boundaries ofan HPDC AM60 alloy by means of EPMA line scanningand reported that the Al concentration varied from 25 wtin the bulk 120572-Mg core to 10wt in the boundary regionIt is to be noted that for the same alloy AM60 Wei andWarren [21] and Barbagallo et al [19] reported differentamount of Al content in the grain boundary region and thisis due to the fact that the casting conditions of the sampleswere different Han et al [22] reported that for permanentmold casting of AZ91D alloy in the dendritic center thealuminum concentration is 26 wt but it is 117 wt atthe dendrite edge about 45 times higher than that in thedendrite center Zhang et al [23] conducted experimentsto compare the amount of microsegregation in permanentmold cast and die-cast AZ91 alloys They reported that theaverage concentration of Al and Zn is lower in the diecasting matrix than in the permanent mold casting matrixAverage concentration of Al is 33 wt and for Zn it is033 wt in permanent mold casting and 3wt Al and022wt Zn in die-cast matrix which means the amount ofsegregationwas higher for comparatively faster cooling Ditzeand Schwerdtfeger [24] reported on strip casting of AZ91alloy that the aluminum content increased from 1wt at thecenter of the dendrite arms where solidification had startedto about 25 wt between the arms where solidificationhad ended Guo et al [25] reported that in AZ80 alloy theregions close to the 120573-Mg

17Al12

eutectic phase have higheraluminum contents and that the maximum concentration inthe dendritic interstice varied between 66 wt and 79 wtThey also reported that applying electromagnetic vibrationon the billet they could increase the value of minimum Alconcentration up to 35 wt from 25 wt which is theminimum concentration of Al in the 120572-Mg matrix in thecenter of a conventional die-cast billet This means that theycould reduce the amount of microsegregation by agitatingthe liquid Table 1 summarizes the available data from theliterature

Segregation takes place due to unequal solute diffusionrates in the solid and the liquid phases of the solventmaterial As a result the phases that solidify in the laterstages of the solidification process such as 120573-Mg

17Al12 are

placed between dendrite arms Gungor [26] reported that theextent of microsegregation in an alloy could be determinedexperimentally by measuring one of the following amount ofnonequilibrium eutectic amount of nonequilibrium secondphase minimum solid composition ratio of minimum andmaximum composition of the primary phase and com-position versus fraction solid profile Experimental tech-niques to investigate the extent of microsegregation includequantitative metallography (point count areal and linealmeasurements) X-ray diffraction analysis [27] and electronmicroprobe measurements

Of the techniques available the most widely used onefor characterizing microsegregation is the random samplingapproach developed by Flemings et al [28] commonly

Journal of Materials 3

known as the point matrix or area scan approach There isno hard and fast rule about the total number of points tobe taken to represent the compositional variability Gungor[26] reported that at least 100 points are necessary to obtaina reasonably accurate result He showed that the result didnot vary significantly if 300 points are taken instead of 100points These points are acquired by means of scanningelectron microscope-energy dispersive spectroscopy (SEM-EDS) or electron microprobe analysis using wavelengthdispersive spectrometry (EPMA-WDS) Two comparativelyless appliedmethods are compositionalmaps and segregationratio With compositional maps it is possible to presentthe nature and variability of the dendritic structure andassociated microsegregation but it is not a suitable methodfor comparing different samplesThe segregation ratio usuallyrefers to the maximum over minimum or the maximumover bulk composition These are the simplest parametersfor comparing different samples but much information islost Martorano and Capocchi [29] used a refined segregationratio and the average deviation between the measurementsand nominal composition were reported

Two approaches were suggested to sort the EPMA datapoints into increasing or decreasing order depending ontheir segregation behavior to produce composition versussolid fraction profiles for each element These approachesare sorting all the measurements based on composition of asingle component (single-element sorts) or sorting based onthe compositional difference between two solutes (differencesorts) Yang et al [30] reported that sorting based on primaryalloying elements can produce more accurate elementalpartition coefficients However the main weakness of bothtechniques lies in the appropriateness of the choice of theelements upon which to base the sort for a 10-componentalloy there are 90 different permutations of the differencesorts to consider [31]

Ganesan et al [31] proposed an alloy-independent sortingalgorithm They termed it weighted interval ranking sort(WIRS) In this approach all elements present at each datapoint are considered along with the measurement errorsaccrued during data treatment By applying this approachfor segregation profiling of Ni-based alloys they demon-strated that this sorting method treats eutectic constituentsappropriately and the errors in the segregation profile arealso more accurately determined The WIRS method wasapplied in this work as this alloy independent sortingmethodcould accurately treat the eutectic constituents of the threeinvestigated multicomponent alloys

Segregation ratio and segregation index these two meth-ods rely on the minima or maxima of an alloying element ata particular location to calculate segregation severity Thesecalculations might be sometimes misleading as only theterminal points of solute profiles are being considered insteadof the entire variation Poirier [32] proposed the segregationdeviation parameter method for measuring the severity ofmicrosegregation This method is better in the sense that thedeviation is calculated over the entire range of data

120590119898=1

1198991198620

119899

sum119894=1

1003816100381610038161003816119862119894 minus 11986201003816100381610038161003816 (1)

In this method the segregation deviation parameter 120590119898

is calculated using (1) The absolute difference between thecomposition at any point 119862

119894and the bulk composition 119862

0is

measured and the sum is taken for all the readingsThen thissummation is divided by the total number of points analyzedand the bulk composition

Both the segregation deviation parameter and the seg-regation index were employed in this work to compare theseverity of microsegregation at different locations of thewedge cast samples

3 Analytical Microsegregation Modeling

Several analytical microsegregation models [27 33ndash38] havebeen found in the literature tomodel the solute redistributionof alloying elements during dendritic solidification of alloysIn most of the models mass balance for the solute elementsis considered within a simplified geometry such as a planecylinder or sphere to describe the growth of dendrite armsIt is obvious from theoretical and experimental evidencethat the simplified geometry gives reasonably accurate resultsfor the majority of alloy systems and solidification pro-cesses [39ndash41]The simplest formulations are the equilibriumsolidification model (lever rule) and Scheil-Gulliver modelwhich describe the two extreme cases of ideal equilibriumand nonequilibrium respectively With the advent of moresophisticated computing technology and improvement ofmaterial databases the more advanced models (Kraft et al[40] Du and Jacot [42] Boettinger et al [43]) incorpo-rate more realistic variable diffusion properties across thesolid-liquid interface Three models will be described inthe following section equilibrium solidification model theScheil-Gulliver solidificationmodel and the Brody-Flemingsdendritic solidification model

31 Equilibrium Solidification Model This model assumesthat a state of equilibrium exists at the solid-liquid inter-face during growth That means there would be negligibleresistance for transportation of atoms between the solid andliquid phases [44] For instance if a single crystal of alloycomposition 119862

0is cooled to temperature (119879lowast) which is

below the liquidus temperature (119879119871) then according to the

equilibrium solidification theory 119862lowast119871and 119862lowast

119878would be the

respective compositions of liquid and solid at the interfaceThe partition coefficient 119870 is the ratio of the compositionof the solid to that of the liquid It indicates the degree ofsegregation of solute The equilibrium partition ratio may bedefined as follows

119870 =119862lowast119878

119862lowast119871

(2)

A value less than unity indicates that the element ispartitioning preferentially to the eutectic region whereasa value greater than unity indicates that the element ispartitioning to the dendrite core as peritectic solidificationThe farther from unity the partition coefficient the morestrongly the element partitions to either the dendrite coreor eutectic region Physical parameters that contribute to


the partition coefficient are differences in atomic radii (thetendency for an element to be in solution) and the chemicalpotential of the elements in the liquid

Applying the equilibrium lever rule the amount of soluteredistribution during equilibrium solidification can be deter-mined by

119862119878119891119878+ 119862119871119891119871= 1198620 (3)

Here 119891119878and 119891

119871are weight fractions of solid and liquid

respectively The above equation can be written in thefollowing form

119862119878=119870 sdot 1198620

(1 minus 119891119878) + 119870 sdot 119891

119878

(4)

This equation describes the composition of the solidphase with respect to the fraction of solid where 119862

119878is solute

concentration in the solid (wt) 1198620is the initial solute

concentration (wt) 119870 is the partition coefficient and 119891119878is

the fraction solidAccording to the assumption of the equilibrium model

there would be complete diffusion in the liquid and solidphases that means the final product would have a homoge-neous composition 119862

119878= 1198620[44]

The dependency of liquidus temperature on the changingliquid composition would result in solidification of the alloysover a range of temperatures The first solid would startforming and the composition would be lower in solute foreutectic alloys compared to initial liquid composition As thesolidification progresses the balance of the solute would berejected enriching the liquid through diffusion This wouldeventually result in lower liquidus temperature than thatof the initial composition This solute rejection process isresponsible for the development of segregation or coring As ageneral rule it can be stated that if the freezing range is largerfor an alloy and it gets sufficient time for solute rejection thesegregation severity would be more [45]

32 Scheil-Gulliver Solidification Model This model is dif-ferent from the equilibrium model in the sense that it doesnot allow any elemental diffusion in the solid This meansthat once a solid is formed nothing comes out of it or getsin This would result in a steady rise in rejected solute levelin the liquid phase until the final liquid region has reachedthe eutectic composition The famous ldquononequilibrium leverrulerdquo or more popularly known as the Scheil equation is asfollows

119862119878= 119870 sdot 119862

0(1 minus 119891

119878)119870minus1

(5)

33 Brody-Fleming Dendritic Solidification Model The workof Bower et al [35] pinpointed the reason for the discrepancybetween experimental microsegregation measurements andthe values predicted by the Scheil model This mismatch isdue to the presence of finite solid-state diffusion in actualcastings whereas the Scheil model assumes no diffusion inthe solid state Therefore the amount of back diffusion thattakes place both during and after solidification has to be

taken into consideration This back diffusion is responsiblefor lower solute levels than the prediction of the Scheilmodel The extent of back diffusion is determined by thedimensionless parameter 120572 as shown in the integration ofthe differential solute balance equation for a parabolic growthrate as follows

119862119878= 119870119862

0[1 minus (1 minus 2120572119870)119891

119878](119870minus1)(1minus2120572119870)

(6)

where

120572 =4119863119878119905119891

1205822 (7)

Here 119863119878is the diffusivity in solid (m2sdotsminus1) 119905

119891is the

local solidification time (s) and 120582 represents the secondarydendrite arm spacing (m) Equation (6) contains two limitingcases that were described earlier for plane front solidificationwhen 120572 is set to 05 then the equation represents theequilibrium lever rule andwhen119863

119878is set to zero (ie no solid

state diffusion) 120572 becomes zero and that results in the Scheilequation

There are many other models available in the literatureand the quest for achieving a perfect model is still going onBut most of these models are modifications of the Brody-Flemings model Kearsey [46] in his thesis came to theconclusion that it is really difficult tomake accuratemicroseg-regation prediction using these simplified models as thesemodels do not take into account the complexity regardingthe number of diffusing solute species and their relativeinteractive effects that takes place during the solidification ofmulticomponent alloys

4 Methodology

The ingots of the three alloys were melted and degased usinghexachloroethane (C

2Cl6) The pouring temperature of the

molten metal in the mold was 1000K or 723∘C Six K-typethermocouples at different locations along the wedge castingwere placed as illustrated in Figure 1(a) Time-temperaturecurveswere obtained at each location using the thermocouplereading The thickness increases gradually from 6mm atlocation 1 to 34mm at location 6 as shown in Figure 1(b) Itis expected that location 1 has the fastest cooling rate whilelocation 6 has the slowest cooling rate of the six locations

The bulk compositions of the investigated alloys arepresented in Table 2 In AE44 alloy rare earth elementswere added as mischmetal The percentage of the rare earthelements in the mischmetal is as follows Ce = 5590 La =3050 Pd = 680 Nd = 520 and others = 160

Solidified samples were sectioned longitudinally at theposition of the thermocouples Samples were ground using120 240 320 400 600 800 and 1200 grit SiC emery paperwhile ethanol was used as lubricant and the samples wereultrasonically cleaned in ethanol between steps to removeany residue Samples were etched with nitric acid reagent(20mL acetic acid 1mL HNO

3(concentrated) 60mL ethy-

lene glycol 20mL water) after being manually polishedThe solidification microstructures were analyzed by opticalmicroscopy (OM) The phase analyses were investigated


12m

m

18m

m24

mm 37

mm 50

mm 68

mm

(a)

Location 1Location 2

Location 3

Location 4

Location 5

Location 634mm

25mm

185mm

12mm9mm6mm

(b)

Figure 1 Schematic of thermocouple positions in the wedge castsample

Figure 2 Schematic of area scanmethod using EDS Each black dotcorresponds to a composition measurement

using scanning electron microscopy (SEM) (Model HitachiS-3400N SEM) equipped with wavelength dispersive spec-trometry (WDS) and energy dispersive spectrometry (EDS)systems for elemental analysis For the SEM the samples werenot etched

The SEM was used mainly in the backscatter electron(BSE) mode at 15 keV BSE images were treated by imageanalysis software in order to enhance the color contrastThe composition measurements for elemental analysis werecarried out using EDS At each sample location a minimumof 150 readings were taken in amatrix using EDS spot analysisas shown in Figure 2

X-ray diffraction (XRD) using XrsquoPert PROmanufacturedby PANalytical Inc was performed to detect the phasespresent in these alloys and measure the volume fraction ofthe dominant secondary phases The samplesrsquo powders wereprepared in a mortar to a uniform particle size distributionSilicon powder (minus325mesh) was added to all powder samplesas an internal standard to correct for any systematic errorX-ray diffraction analysis of the sampleswas carried out using

minus30minus20minus10

0102030

400450500550600650

0

10

20

30

6 10 14 18 22 26 30Time (s)

6 10 14 18 22 26 30Time (s)

6 10 14 18 22 26 30Time (s)

Liquidus

Solidus

d2Tdt2

)∘ C2

sminus2

Tem

pera

ture

(∘C)

dTdt (

(

)C

sminus1

Figure 3 The cooling first and second derivative curves of theAZ91D alloy showing the solidus and liquidus

XrsquoPert High Score Plus software in combination with theRietveld analysis and Pearsonrsquos crystal database [47]

Secondary dendrite arm spacing was measured using thelinear intercept method from optical micrographs Suitablelocations were selected where secondary dendrite arms areclearly distinguishable Then the average secondary dendritearm spacing was measured by counting the number of armsintercepting a straight line of a known length Readings weretaken at 10 different locations close to the thermocoupleposition in the wedge and then averaged

5 Results and Discussion

51 Thermal Analysis The cooling curves obtained at dif-ferent locations of the wedge cast samples were analyzedto obtain important thermal parameters A cooling curvecontains information regarding the release of heat duringsolidification This release of heat eventually changes theslope of the cooling curve which indicates the characteristicsof transformation and phase reactions during solidificationHowever the amount of the heat that evolved during somephase transformations is very small that it is difficult to detectthese changes from the cooling curve alone Hence the firstand second derivatives of the cooling curve were employed todetermine these thermal parameters accurately This proce-dure is presented in Figure 3 for location 1 ofAZ91D alloyTheblock arrows denote the approximate start and end of solidi-fication as determined from temperatures at deviations from


Table 1 Summary of the literature data

Alloy Casting condition Min Al wt Max Al wt Scheil model ReferenceMin Al wt Max Al wt

Mg-4Al-4Ca DSlowast 1 gt3 1 3AZ31 DS 1 4-5 1 gt6 [7]AM50 DS lt2 8-9 lt2 gt10 [8 9]Mg-4Al DS lt2 8-9 lt2 gt10AM60 HPDClowastlowast 25 10 mdash mdash [10]AM50A Die casting 15 30 mdash mdash [19]AM60A Die casting 2 40 mdash mdash [21]AZ91D PMClowastlowastlowast 26 117 mdash mdashAZ91D PMC 33 mdash mdash mdash [22]AZ91D Die casting 3 mdash mdash mdash [23]AZ91D Strip casting 1 25 mdash mdashAZ80 Die-cast billet 25ndash35 66ndash79 mdash mdash [24]lowastDS directional solidification lowastlowastHPCD high-pressure die casting lowastlowastlowastPMC permanent mold casting

Table 2 Bulk composition of the investigated alloys (wt)

Alloy Al Zn Mn Si Cu Fe Ce (RElowast)AE44 395 019 03 0007 lt0005 lt0005 220 (394lowast)AM60B 57 0023 031 0013 lt0005 lt0005AZ91D 88 075 034 0015 lt0005 lt0005lowastPercentage of the other rare earth elements in the mischmetal

Table 3 Liquidus solidus and freezing range calculation of thethree alloys

Alloy Liquidus (∘C) Solidus (∘C) Freezing range (∘C)AZ91D 600 410 190AM60B 620 415 205AE44 630 575 55

Table 4 Cooling rate of investigated alloys within the solidificationrange

LocationCooling rate ∘Cs

AZ91D(600∘Cndash410∘C)

AM60B(620∘Cndash415∘C)

AE44(630∘Cndash575∘C)

1 1011 1613 6052 1132 1655 7793 1141 16 7264 1015 1187 5845 808 817 3016 518 502 149

linearity in the first and second derivative curves The resultsare summarized in Table 3 The liquidus and solidus temper-atures recorded at different wedge locations remain constantregardless of the change of cooling rate From Table 3it can be seen that the rare earth containing alloys have thesmallest solidification range

The cooling rates of the three investigated alloys atdifferent thermocouple locations are presented in Table 4For ease of calculation and representation cooling rates were

considered to be changing linearly within the approximatesolidification range of the alloys A little difference in coolingrate among the first three locations was noticed Althoughit is considered that cooling rate decreases gradually fromlocation 1 to location 6 it is evident from the table thatfor all three alloys the cooling rate at location 2 is slightlyhigher than that at location 1 The deviation observed atthese thermocouple locations can possibly be explained bysome phenomenological factors Firstly this could be dueto the delay in thermocouple response to correctly recordthe temperature change in rapidly cooled locations Secondlythe pattern of mold filling might also be responsible Thewedge cast sample is very narrow at the bottom and hencethis narrow end could solidify much earlier before the rest ofthe locations But the molten metal on top of this solidifiedlocation will affect its cooling rate Thirdly this thin endat the bottom of wedge might not be cooled properly bythe circulating cooling water due to stagnation Howeversamples with the same cooling rate might have differentamounts ofmicrosegregation based on cooling and solidifica-tion conditions such as thickness of sample coarsening andhomogenization period

52Microstructural Analysis Themicrostructure of the threestudied magnesium alloys was characterized by quantifyingthe area percentage of the secondary phases average sizeof the secondary phase particles the maximum size of thesecondary phase particles and the secondary dendrite armspacing All these microstructural features vary significantlywith the change in cooling rate and subsequentmicrosegrega-tion The BSE micrographs were taken at 500x magnification


Table5Microstructuralmapping

ofAZ9

1DA

M60B

andAE4

4alloys

andtheird

etailsin

locatio

ns1and

6Th

epicturesw

eretaken

atmagnificationof

100X

Allo

yLo

catio

nDetails

Edge

ofthew

edge

Colum

nartoequiaxed

transition

Centero

fthe

wedge

AZ9

1D

1

100120583

m

6

AM60B

1 6

AE4

4

1 6


120572-Mg matrix

Discontinuousprecipitates

120573-Mg17Al12

50120583m

Al8Mn5

(a)

120573-Mg17Al12

120572-Mg matrix

50120583m

Mn-rich phase

(b)

120572-Mg matrix

Al3REAl11RE3

50120583m

(c)

Figure 4 General microstructure of the as-cast (a) AZ91D alloy (b) AM60B (c) AE44 regardless of the thermocouple location

for image analysis and each micrograph covers an area of227120583m times 200120583m Measurement of average and maximumsize of secondary phase particles at specific locations providesinformation regarding overall particle size distribution

Microstructural mapping was done from edge to edge forthe first four thermocouple positions For locations 5 and 6as they are much wider pictures were taken from the centerto the edge of the wedge instead of the regular patternededge to edge Microstructural maps and important segmentsare shown in Table 5 For each location of the wedge thesemerged micrographic maps are divided into three sectionsedge transition from columnar to equiaxed andmidpositionof the wedge

The general microstructure of the as-cast Mg alloys isdemonstrated in Figure 4 AZ91D alloy is characterized by asolid solution of aluminum in magnesium which is knownas 120572-Mg (hexagonal close packed structure) and eutectic 120573-Mg17Al12

phase Dendrite arms of 120572-Mg are surrounded bya eutectic mixture of 120572 and 120573-Mg

17Al12

In addition to thisa small amount of Al

8Mn5is also noticed within the 120572-

Mg matrix These phases are shown in Figure 4(a) The 120573-Mg17Al12phase may be fully or partially divorced depending

on the solidification rate The typical microstructure ofAM60B alloy that consisted of 120572-Mg dendrite cells anda divorced-eutectic (120572-Mg + 120573-Mg

17Al12) is presented in

Figure 4(b) A few spherical Mn-rich intermetallic parti-cles are also generally observed in the microstructure Theprimary 120572-Mg dendrites that form the largest portion ofthe microstructure are surrounded by divorced eutecticA typical microstructure of AE44 alloy that consisted of

primary 120572-Mg dendrites and intermetallic phases in theinterdendritic regions or at grain boundaries is presented inFigure 4(c)

The intermetallic phases have two distinctive morpholo-gies one is a lamellar or needle-like acicular morphologyand the other is of a particulate or globular shape Thelamellar phase is identified as Al

11RE3and the particulate

shaped particles are Al3RE Al

11RE3is the dominant phase

in all wedge locations the presence of Al3RE is in very small

amountsFigure 5 shows SEM micrographs of the midpositions of

the wedge at locations 1 and 6 of the three Mg alloysFor AZ91D alloy the size of the secondary phase particles

increases significantly from location 1 to location 6 Althoughthe sizes of the particles are much smaller in location 1their number is much greater in comparison to location 6The distance between eutectic 120573-Mg

17Al12

phase particlesalso increases with the decrease of cooling rate whichindicates that secondary dendrite arm spacing is varyingwith cooling rate For AM60B a fully divorced morphologywas observed for the 120573-Mg

17Al12

phase in all locations Thepresence of coring was more obvious in locations 5 and 6The size of individual secondary phase particles increasedsignificantly from location 1 to location 6 and subsequentlythe number of these particles decreased For AE44 alloylocations 1 2 and 3 have a similar cluster-like morphol-ogy of Al

11RE3 Then from location 4 the space between

the clusters starts to increase This transition continues inlocations 5 and 6 where the morphology shows scatteredclusters


AZ91D-location 1 AZ91D-location 6

(a)

AM60B-location 1 AM60B-location 6

(b)

AE44-location 1 AE44-location 6

(c)

Figure 5 Microstructures at the midposition of the wedge at locations 1 and 6 for AZ91D AM60B and AE44 alloys

The variation in secondary dendrite arm spacing (SDAS)measured close to the six thermocouple locations forthe three Mg alloys is shown in Figures 6(a)ndash6(c) Thevariation of SDASwith the change of cooling rate for the threeMg alloys was calculated It is concluded that the secondarydendrite arm spacing increases as the cooling rate decreasesfrom around 9 120583m at location 1 up to about 26120583m at location6 for AZ91D alloy For AM60B alloy the SDAS increasedgradually with the decrease in cooling rate from 15120583m atlocation 1 up to 30 120583m at location 6 The SDAS variation forAE44was in the range of 10ndash15 120583mat location 1 and increasedup to 45 120583m at location 6 due to significant reduction incooling rate

53 Microsegregation Measurements Quantitative microseg-regation analysis was carried out close to the six thermo-couple locations for the three investigated magnesium alloys

The following results were obtained from the acquired data atdifferent locations of the wedge solute redistribution profilefor alloying elements (experimental andmodeling) partitioncoefficient segregation index (ratio between minima andbulk composition) and segregation deviation parameter (120590

119898)

and area percentage of eutectic from the distribution pro-files Inhomogeneous distribution of solute elements duringdendritic solidification of an alloy takes place due to coringCoring or layered structure solidification is the key conceptfor understanding microsegregation As can be seen fromthe schematic diagram of a dendrite arm in Figure 7(a) thechemical composition at point ldquoCrdquo is different from the chem-ical composition of point ldquoErdquo It is assumed that solidificationstarts at point ldquoCrdquo and finishes at point ldquoErdquo and the change inchemical composition is gradual In Figure 7(b) the opticalmicrograph of AZ91D alloy is presented to be compared withthe schematic diagram


0

5

10

15

20

25

30

0 10 20 30 40 50 60 70

Wedge locationD

endr

ite ar

m sp

acin

g (120583

m)

Distance from bottom of wedge (mm)

1 2 3 4 5 6

(a)

0

5

10

15

20

25

30

35

0 10 20 30 40 50 60 70

Wedge location

Den

drite

arm

spac

ing

(120583m)


1 2 3 4 5 6

(b)

0

10

20

30

40

50

60

0 20 40 60

Wedge location

Den

drite

arm

spac

ing

(120583m)


1 2 3 4 5 6

(c)

Figure 6 Secondary dendritic arm spacing measured at center of the wedge of (a) AZ91D (b) AM60B (c) AE44 at different locations

C

E

(a)

C

(b)

Figure 7 Coring in dendritic solidification (a) schematic of dendrite arm and (b) dendritic microstructure in optical micrograph of AZ91Dalloy


0

5

10

15

20

25

30

35

60 70 80 90 100

AZ91D

Zn

AlMn

(wt

)

Magnesium (wt)

(a)

0

5

10

15

20

25

30

70 80 90 100

AM60B

Mn

(wt

)

Magnesium (wt)

Al

(b)

(wt

)

Magnesium (wt)

0

1

2

3

4

5

6

7

8

80 85 90 95 100

AE44

AlLa

CeNd

(c)

Figure 8 Segregation trend in investigated alloys

When the molten alloy starts to solidify at point ldquoCrdquo thewt of aluminum can be as low as 2 or 3wt depending onthe cooling rate And it gradually increases to the last point tobe solidified namely point ldquoErdquo Some alloying elements havea tendency to accumulate in higher concentration at the edgeof the dendritic arm These elements have low concentrationat the center of the arm Some alloying elements behave in theopposite way they have higher concentration at themiddle ofdendrite arm and then gradually decrease towards the edgeThis was mainly reported for the elements forming peritecticsystems

531 Solute Redistribution In this work microsegregationmeasurements were performed using SEMEDS 150 readingswere taken in a 10 times 15 regular grid with a spacing of10 120583m between each point All the data points were sorted

based on the weighted interval ranking sort (WIRS) method[31] The alloying elements which were present in less than05 wt in the bulk composition of the alloy were neglectedbecause they are below the EDS detection limit This couldbe the major source of the experimental errors which leadto provision of different values of the calculated parametersIn this work the microsegregation analysis was carried outfor aluminum and zinc in AZ91D aluminum andmanganesein AM60B and aluminum cerium and lanthanum in AE44The segregation trend of these alloys for all locations in thecasting is presented in Figure 8

For AZ91D and AM60B with the increase of magnesiumconcentration the concentration of Al and Zn decreaseswhile Mn shows the opposite trend This means that Al andZn would be low in the dendrite core and gradually increasetowards the dendrite periphery For AE44 alloy with theincrease of Mg concentration all other elements Al La Ce


0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AZ91D-location 1

(a)

0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AZ91D-location 6

(b)

0

04

08

12

16

2

0 02 04 06 08 1

Zn (w

t)

Fraction solid

(c)

0

05

1

15

2

25

3

0 02 04 06 08 1

Zn (w

t)

Fraction solid

(d)

Figure 9 Solute redistribution in locations 1 and 6 of AZ91D alloy

and Nd decrease in concentrationThus the concentration ofthese elements will be low in the dendrite core

The Brody-Fleming equation [35] was used for modelingthe solute redistribution profile modeling

The parameters needed to calculate the solute profiles(composition at any specific point solidified 119862

119878) using this

model are dimensionless parameter 120572 solid fraction 119891119878 par-

tition coefficient119870 and bulk composition 1198620 The secondary

dendrite arm spacing and solidification time at each locationwere used from the experimental data to calculate120572 From theexperimentally measured data sorted by the WIRS methodvalues of 119862

119878and 119891

119878can be obtained Putting these values in

the Scheil equation (2) values of the partition coefficient 119870were calculated

The average value of 119870 was then used in the Brody-Fleming model for drawing solute redistribution profiles forthe three Mg alloys in all locations These experimentallyobtained values of119870 for all major alloying elements are listedin Table 6 From the table it is clear that the average valueof the partition coefficient decreases with the decrease ofcooling rate

The solute redistribution profiles at locations 1 and 6 forthe major alloying elements of AZ91D AM60B and AE44

are shown in Figures 9 10 and 11 respectively Open symbolsrepresent the solute profile obtained from the experimentaldata sorted and treated by the WIRS method and the closedsymbols represent the curves calculated using the Brody-Fleming model [35]

For AZ91D the average value of 119870Al is 053 at loca-tion 1 and 043 at location 6 However Shang et al [48]reported 119870Al = 035 and 119870Zn = 009 for the Scheiland equilibrium cooling They also reported that for theScheil cooling conditions the partition coefficient remainsconstant up to 085 fractions solid For AM60B the averagevalue of 119870Al is 056 at location 1 and 041 at location 6Although in many solute redistribution models the partitioncoefficient value is considered to be the same for the Scheiland equilibriumcooling conditions the results obtained fromthese experiments indicate that partition coefficient valuechanges significantly with cooling rate

For AE44 the average value of 119870Al at location 1 is 034and at location 6 it decreases to 023 For Ce and La thepartition coefficient is too small which could be due to theirlow solubility in Mg For Ce at location 1 the average 119870is 0068 and at location 6 it is 00257 For La at location 1the average is 0075 and at location 6 the average is 00283


0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AM60B-location 1

(a)

0

5

10

15

20

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AM60B-location 6

(b)

0

01

02

03

04

05

0 02 04 06 08 1

Mn

(wt

)

Fraction solid

(c)

0

01

02

03

04

05

0 02 04 06 08 1

Mn

(wt

)

Fraction solid

(d)

Figure 10 Solute redistribution in locations 1 and 6 of AM60B alloy

Chia et al [49] reported the partition coefficient for La andCe using the binary phase diagrams of Mg-Ce and Mg-Laas 00193 and 0036 respectively Their partition coefficientvalues were closer to what has been obtained in slowercooling locations in this work For both Ce and La at location6 the partition coefficient is 003

532 Area Percentage Calculations of Secondary PhasesAccording to theMg-Al binary phase diagram themaximumsolubility of Al in Mg is around 129 wt On the basis ofthis assumption the area fraction of 120573-Mg

17Al12

phase wasmeasured using the solute redistribution curve of aluminumat different wedge locations for AZ91D and AM60B alloys Inthismethod a horizontal line is extended from themaximumAl solubility value A vertical line is constructed at the end ofthe linear proportion of the fraction solid curve The amountof the eutectic then can be calculated based on the differencebetween the fraction solid curve and the constructed verticallineThe procedure applied for these calculations is presentedin Figure 12

The eutectic area percentage was obtained through imageanalysis and the solute redistribution curve of aluminum forthe three Mg alloys In this work 120573-Mg

17Al12

is considered

the eutectic phase in the AZ91D and AM60B alloys Noeutectic phase was formed in the AE44 alloy and thus bothAl3RE andAl

11RE3were the so-called secondary precipitates

Hence for the three alloys the 120572-Mg matrix was consideredthe primary phase and all other particles were called thesecondary phase The area percent distribution of secondaryphases measured from the solute redistribution curve andimage analysis are available in Table 7 Accordingly the eutec-tic area percentage of AZ91D alloy increases with cooling rateup to location 4 and then decreases at locations 5 and 6 Thistrend is similar to observation by image analysis For AM60Bat sample locations 1 2 and 3 the area fraction was in therange of 35ndash5 Afterwards a reduction was observed atlocations 5 and 6 At location 6 it was only 2

In AE44 the composition of Al is very low in 120572-Mgmatrix as most of the aluminum reacts with the rare earthelements to form precipitates Solubility of La Ce and Ndis also very low in the matrix Hence the maximum solidsolubility of La in Mg 08 wt was assumed as the beginningof precipitate formation For AE44 alloy area percentage ofsecondary precipitates decreases gradually with cooling ratefrom 30 at location 1 to 8 at location 6 Hehmann et al[50] reported that the solid solubility of Al La and Ce in


0

2

4

6

8

10

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AE44-location 1

(a)

0

2

4

6

8

10

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AE44-location 6

(b)

0

2

4

6

8

10

0 02 04 06 08 1

Ce (

wt

)

Fraction solid

(c)

0

2

4

6

0 02 04 06 08 1

Ce (

wt

)

Fraction solid

(d)

0

1

2

3

4

5

0 02 04 06 08 1

La (w

t)

Fraction solid

(e)

0

1

2

3

0 02 04 06 08 1

La (w

t)

Fraction solid

(f)

Figure 11 Solute redistribution in locations 1 and 6 of AE44 alloy

Mg could be increased by rapid solidification method Henceincreased solid solubility in 120572-Mg matrix will result in lowerarea percentage of eutectic phases In the present experimentvery high cooling rate was observed at locations close tobottom of the wedge therefore it could affect the maximumsolid solubility of other alloying elements in magnesiumThis means that if accurate values of solid solubility areused to calculate the area percentage the difference betweenimage analysis and the solute distribution curve method maybecome less

533 Segregation Index and Minimum Composition Thesegregation index is the ratio between the minimum com-position and bulk composition of an alloying element Todetermine the minimum at a specific location the averageof the ten lowest compositions was taken The minimumconcentration of aluminum and the segregation index atdifferent wedge locations for the three alloys are presented inTable 8 From the table it can be seen that as the cooling ratedecreases theminimumcomposition decreases and hence theseverity of segregation increases For AZ91D the minimum


Table 6 Effective partition coefficient for major alloying elements in the investigated alloys

Location AZ91D AM60B AE44119870Al 119870Zn 119870Al 119870Mn 119870Al 119870Ce 119870La

1Lowest 042 004 048 003 029 002 002Highest 058 050 068 073 042 014 015Average 053 021 056 030 034 007 008






lowastlowastUsing FactSage software119870Al = 035119870Zn = 009119870Ce = 00193119870La = 0036 and119870Mn = 110

Table 7 Area percentage of secondary phases measured from solute redistribution curve and image analysis for the investigated alloys

Location AZ91D AM60B AE44Solute curve Image analysis Solute curve Image analysis Solute curve Image analysis

1 75 55 34 16 30 2082 76 58 40 16 24 2103 8 65 50 21 22 1784 10 71 40 21 12 1325 7 65 27 19 12 926 66 45 20 17 8 86

concentration of aluminum decreases with the decrease ofcooling rate At location 1 the composition is 36 wt andat location 6 it drops to 301 wt For AM60B at location1 minimum concentration of aluminum is 25 wt and atlocation 6 it reduces to 18 wt For AE44 at location 1the minimum concentration of aluminum is 11 wt and atlocations 6 the concentration is 09 wt

534 Segregation Deviation The severity of microsegrega-tion is measured by the segregation deviation parameter(120590119898) using (1) Martorano and Capocchi [29] reported that

microsegregation severity is lower for columnar dendritesthan for equiaxed ones It has also been reported that theincrease in segregation deviation parameter 120590

119898 for a change

in structure fromcolumnar to equiaxed seems to be constantapproximately 011 for the Cu-8wt Sn alloys However thisvalue can be applicable for any particular system since itshows the difference in the amount of segregation betweencolumnar and equiaxed segregation Consequently the typeof dendritic growth seems to be an important variableto define microsegregation The greater microsegregationseverity observed in an equiaxed dendrite zone comparedwith that in columnar dendrites might be the result of morehomogenization in the latter structure The overall deviationfrom the bulk composition for aluminum is presented inFigure 13

In the present work location 1 could be considered ascolumnar dendritic and location 6 could be considered as


Table 8 Minimum concentration of aluminum and segregation index for the investigated alloys at different locations

Location AZ91D AM60B AE44Minimum Al Segregation index Minimum Al Segregation index Minimum Al Segregation index

1 363 242 256 223 115 3442 357 247 225 254 121 3273 354 249 219 261 130 3044 290 303 189 301 106 3735 312 282 205 278 107 3696 301 293 184 310 090 439

0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

Eutectic129 wt

Primary 120572-Mg matrix

Figure 12 Procedure for the eutectic fraction calculation using thesolute redistribution curve

03

04

05

06

07

0 10 20 30 40 50 60 70

Wedge location

Distance from the bottom of the wedge (mm)

AZ91DAM60BAE44

Segr

egat

ion

devi

atio

n(120590

m)

1 2 3 4 5

Figure 13 Segregation deviation for three investigated alloys

equiaxed dendriticThe difference in deviation from location1 to location 6 forAZ91DAM60B andAE44 is 008 006 and019 respectively which is comparable to the results observedby Martorano and Capocchi [29]

For AM60B alloy from location 1 to location 5 thesegregation deviation increases and then it slightly decreasesat location 6 thus contradicting the segregation indexThe segregation index is high at location 6 but when thesegregation deviation is calculated on a broader range the

segregation deviation is comparatively lower than at otherlocations

6 Summary

ThreemainMg alloys (AZ91D AM60B and AE44) solidifiedin a range of cooling rates (1ndash20∘Cmin) were studied andfound to exhibit dendritic microstructures At higher coolingrate (locations 1 and 2) the dendritic morphology waspredominantly columnar and at lower cooling rate (locations5 and 6) dendritic equiaxed morphology was observedSecondary dendrite arm spacing increased significantly withthe decrease of cooling rate for all three investigated alloysThe arm spacing ranges for the different alloys are 10 to25 120583m for AZ91D 15 to 30 120583m for AM60B and 10 to 45 120583mfor AE44 The average size of secondary phase particlesincreased substantially with the decrease of cooling rateFor AZ91D the 120573-Mg

17Al12

phase had a partially divorcedmorphology at fast cooled locations of the wedge and fullydivorced morphology at slowly cooled locations For AE44the secondary precipitates had cluster-like morphology atfaster cooling rate and gradually becamemore dispersed withslower cooling rate

Microsegregation was more pronounced at slow cooledlocations which is evident from themicrosegregation param-eters The minimum concentration of aluminum was alwayslow for slow cooled locations (3 wt at location 6 in compar-ison to 36 wt at location 1 for AZ91D alloy) Significant dif-ference in segregation deviation (Δ120590

119898) was observed between

the columnar and the equiaxed dendrites approximately inthe range of (006ndash019) for the three alloys The highersegregation deviation observed in equiaxed morphology isprobably due to prolonged back diffusion which takes placeat slow cooling rates

Experimentally obtained solute redistribution profilesmatch reasonably with theoretically calculated profiles exceptat very low solid fraction This discrepancy at low solidfraction is possibly due to the presence of a few primarydendritic arms in the microstructure which have lowerconcentration of aluminum than the rest of the matrix Theelemental partition coefficients calculated from the experi-mentally obtained redistribution profiles were comparativelyhigher than the partition coefficients calculated from binaryphase diagrams

Area fraction of secondary phase particles measuredby two different methods image analysis and solute


redistribution curves showed close resemblance Areafraction measured from solute redistribution curves iscomparatively higher due to the fact that in case of imageanalysis only the secondary phase particles are measuredbased on color threshold while in solute curve methodregions adjacent to particles which have high concentrationof alloying elements (eg eutectic phases) are also taken intoaccount

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgment

The authors would like to acknowledge AUTO21 NSERCStrategic Network of Excellence for the financial support ofthis work

References

[1] A Boby U Pillai B Pillai and B Pai ldquoDevelopments inmagnesium alloys for transport applicationsmdashan overviewrdquoIndian Foundry Journal vol 57 p 30 2011

[2] R S Beals C Tissington X Zhang et al ldquoMagnesium globaldevelopment outcomes from the TMS 2007 annual meetingrdquoJournal of theMinerals Metals andMaterials Society vol 59 no8 pp 39ndash42 2007

[3] G Davies Materials for Automobile Bodies Butterworth-Heinemann Oxford UK 2003

[4] H Mao V Chandrasekar M Murray et al ldquoMicrostructuralcharacteristics of die cast AZ91D andAM60magnesium alloysrdquoTech Rep SAE 1996

[5] E Aghion B Bronfin and D Eliezer ldquoThe role of the mag-nesium industry in protecting the environmentrdquo Journal ofMaterials Processing Technology vol 117 no 3 pp 381ndash385 2001

[6] J Quaresma C Santos and A Garcia ldquoCorrelation betweenunsteady-state solidification conditions dendrite spacings andmechanical properties of AI-Cu alloysrdquoMetallurgical andMate-rials Transactions A vol 31 no 12 pp 3167ndash3178 2000

[7] X Zheng A Luo C Zhang J Dong and R Waldo ldquoDirec-tional solidification and microsegregation in a magnesium-aluminum-calcium alloyrdquoMetallurgical and Materials Transac-tions A vol 43 no 9 pp 3239ndash3248 2012

[8] D Mirkovic and R Schmid-Fetzer ldquoDirectional solidificationof Mg-Al alloys and microsegregation study of Mg alloys AZ31and AM50mdashpart I methodologyrdquo Metallurgical and MaterialsTransactions A vol 40 no 4 pp 958ndash973 2009

[9] D Mirkovic and R Schmid-Fetzer ldquoDirectional solidificationof Mg-Al alloys and microsegregation study of Mg alloys AZ31and AM50mdashpart II comparison between Az31 and AM50rdquoMetallurgical and Materials Transactions A vol 40 no 4 pp974ndash981 2009

[10] C Zhang DMa K SWu et al ldquoMicrostructure andmicroseg-regation in directionally solidifiedMg-4Al alloyrdquo Intermetallicsvol 15 no 10 pp 1395ndash1400 2007

[11] A Luo ldquoUnderstanding the solidification ofmagnesium alloysrdquoin Proceedings of the 3rd International Magnesium Conferencepp 449ndash464 Manchester UK 1997

[12] D H Stjohn A K Dahle T Abbott M D Nave and M QianldquoSolidification of cast magnesium alloysrdquo in Proceedings of theMinerals Metals and Materials Society (TMS rsquo03) pp 95ndash100Magnesium Technology San Diego Calif USA 2003

[13] Y W Riddle and M M Makhlouf ldquoCharacterizing solidifica-tion by nonequilibrium thermal analysisrdquo in Proceedings of theMinerals Metals and Materials Society (TMS rsquo03) pp 101ndash106Magnesium Technology San Diego Calif USA 2003

[14] A Lindemann J Schmidt M Todte and T Zeuner ldquoThermalanalytical investigations of the magnesium alloys AM60 andAZ91 including the melting rangerdquo Thermochimica Acta vol382 no 1-2 pp 269ndash275 2002

[15] M Ohno D Mirkovic and R Schmid-Fetzer ldquoOn liquidus andsolidus temperatures inAZ andAMalloysrdquo in Proceedings of theMinerals Metals and Materials Society (TMS rsquo06) pp 129ndash132San Antonio Tex USA 2006

[16] M D Nave A K Dahle and D H StJohn ldquoEutectic growthmorphologies in magnesium-aluminium alloysrdquo in Proceedingsof theMineralsMetals andMaterials Society (TMS rsquo02) pp 233ndash242 Nashville Tenn USA 2000

[17] L P Barber ldquoCharacterization of the solidification behaviorand resultantmicrostructures ofmagnesium-aluminum alloysrdquoin Materials Science and Engineering Worcester PolytechnicInstitute Worcester Mass USA 2004

[18] A K Dahle Y C Lee M D Nave P L Schaffer and DH Stjohn ldquoDevelopment of the as-cast microstructure inmagnesium-aluminium alloysrdquo Journal of Light Metals vol 1no 1 pp 61ndash72 2001

[19] S Barbagallo H Laukli O Lohne and E Cerri ldquoDivorcedeutectic in a HPDC magnesium-aluminum alloyrdquo Journal ofAlloys and Compounds vol 378 no 1-2 pp 226ndash232 2004

[20] MN KhanM Aljarrah J TWood andMMedraj ldquoThe effectof cooling rate on thermophysical properties of magnesiumalloysrdquo Journal of Materials Research vol 26 no 8 pp 974ndash9822011

[21] L-Y Wei and R Warren ldquoMicrostructural characterisation ofseveral magnesium alloys in AM seriesrdquo Materials Science andTechnology vol 23 no 6 pp 745ndash752 2007

[22] Q Han E Kenik S Agnew and S Viswanathan ldquoSolidificationbehaviour of commercial magnesium alloysrdquo in MagnesiumTechnology pp 81ndash86TheMineralsMetals ampMaterials SocietyWarrendale Pa USA 2001

[23] Z Zhang A Couture R Tremblay and D Dube ldquoMicrostruc-ture and mechanical properties of permanent mold and diecasting of AZ 91 magnesium alloyrdquo in Proceedings of the Inter-national Symposium on Light Metals pp 397ndash406 CanadianInstitute of Mining Metallurgy and Petroleum 1999

[24] A Ditze and K Schwerdtfeger ldquoStrip casting of magnesiumwith the single-belt processrdquo Scandinavian Journal of Metal-lurgy vol 32 no 6 pp 311ndash316 2003

[25] S Guo Q Le Y Han Z Zhao and J Cui ldquoThe effect of theelectromagnetic vibration on the microstructure segregationand mechanical properties of As-cast AZ80 magnesium alloybilletrdquo Metallurgical and Materials Transactions A vol 37 no12 pp 3715ndash3724 2006

[26] M Gungor ldquoA statistically significant experimental techniquefor investigating microsegregation in cast alloysrdquo MetallurgicalTransactions A vol 20 no 11 pp 2529ndash2533 1989

[27] J Sarreal and G Abbaschian ldquoThe effect of solidification rateon microsegregationrdquo Metallurgical Transactions A vol 17 no11 pp 2063ndash2073 1986


[28] M C Flemings D R Poirier R V Barone and H D BrodyldquoMicrosegregation in Iron base alloysrdquo Journal of Iron and SteelInstitute vol 208 pp 371ndash381 1970

[29] M Martorano and J Capocchi ldquoEffects of processing variableson the microsegregation of directionally cast samplesrdquo Metal-lurgical and Materials Transactions A vol 31 no 12 pp 3137ndash3148 2000

[30] W Yang K-M Chang W Chen S Mannan and J Debar-badillo ldquoMonte carlo sampling for microsegregation measure-ments in cast structuresrdquo Metallurgical and Materials Transac-tions A vol 31 no 10 pp 2569ndash2574 2000

[31] M Ganesan D Dye and P Lee ldquoA technique for characterizingmicrosegregation in multicomponent alloys and its applicationto single-crystal superalloy castingsrdquoMetallurgical and Materi-als Transactions A vol 36 no 8 pp 2191ndash2204 2005

[32] D R Poirier Microsegregation in Ternary Iron-Carbon-Chromium Alloys Department of Metallurgy MassachusettsInstitute of Technology Cambridge Mass USA 1966

[33] E Scheil ldquoBemerkungen zur schichtkristallbildungrdquo ZeitschriftMetallkunde vol 34 pp 70ndash72 1942

[34] T Clyne and W Kurz ldquoSolute redistribution during solidifica-tion with rapid solid state diffusionrdquoMetallurgical TransactionsA vol 12 no 6 pp 965ndash971 1981

[35] T Bower H Brody and M Flemings ldquoMeasurements of soluteredistribution in dendritic solidificationrdquo Transaction of theMetallurgical Society of AIME vol 236 pp 624ndash633 1966

[36] I Ohnaka ldquo Mathematical analysis of solute redistributionduring solidification with diffusion in solid phaserdquoTransactionsof the Iron and Steel Institute of Japan vol 26 no 12 pp 1045ndash1051 1986

[37] S Kobayashi ldquoA mathematical model for solute redistributionduring dendritic solidificationrdquo Transactions of the Iron andSteel Institute of Japan vol 28 pp 535ndash542 1988

[38] L Nastac and D M Stefanescu ldquoAn analytical model forsolute redistribution during solidification of planar columnaror equiaxed morphologyrdquoMetallurgical Transactions A vol 24no 9 pp 2107ndash2118 1993

[39] J Lacaze P Benigni and A Howe ldquoSome issues concerningexperiments and models for alloy microsegregationrdquo AdvancedEngineering Materials vol 5 no 1-2 pp 37ndash46 2003

[40] T Kraft M Rettenmayr and H Exner ldquoAn extended numericalprocedure for predicting microstructure and microsegregationof multicomponent alloysrdquo Modelling and Simulation in Mate-rials Science and Engineering vol 4 no 2 pp 161ndash177 1996

[41] F Y Xie T Kraft Y Zuo C H Moon and Y A ChangldquoMicrostructure and microsegregation in Al-rich Al-Cu-Mgalloysrdquo Acta Materialia vol 47 no 2 pp 489ndash500 1999

[42] Q Du and A Jacot ldquoA two-dimensional microsegregationmodel for the description of microstructure formation dur-ing solidification in multicomponent alloys formulation andbehaviour of the modelrdquo Acta Materialia vol 53 no 12 pp3479ndash3493 2005

[43] W J Boettinger U R Kattner and D K Banerjee ldquoAnalysisof solidification path and microsegregation in multicomponentalloysrdquo in Modelling of Casting Welding and Advanced Solidifi-cation Processed-VIII B G Thomas and C Beckermann Edsvol 1 pp 159ndash170 TMS Warrendale Pa USA 1998

[44] M C Flemings Solidification Processing McGraw-Hill 1974[45] MC Flemings ldquoSolidification processingrdquoMetallurgical Trans-

actions vol 5 no 10 pp 2121ndash2134 1974

[46] R M Kearsey ldquoCompositional effects on microsegregationbehaviour in single crystal superalloy systemsrdquo in Mechani-cal and Aerospace Engineering Carleton University OntarioCanada 2004

[47] H Putz and K Brandenburg Pearsonrsquos Crystal Data CrystalStructure Database for Inorganic Compounds

[48] S Shang H Zhang S Ganeshan and Z-K Liu ldquoThe develop-ment and application of a thermodynamic database for mag-nesium alloysrdquo Journal of the Minerals Metals and MaterialsSociety vol 60 no 12 pp 45ndash47 2008

[49] T L Chia M A Easton S M Zhu M A Gibson NBirbilis and J F Nie ldquoThe effect of alloy composition on themicrostructure and tensile properties of binary Mg-rare earthalloysrdquo Intermetallics vol 17 no 7 pp 481ndash490 2009

[50] F Hehmann F Sommer and B Predel ldquoExtension of solidsolubility in magnesium by rapid solidificationrdquo MaterialsScience and Engineering A vol 125 no 2 pp 249ndash265 1990

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014


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MetallurgyJournal of

BioMed Research International



Volume 2014

MaterialsJournal of

Nano

materials


Journal ofNanomaterials


solidification such as the amount and distribution of eutec-tic phases grain size dendrite spacing and porosity [6]Segregation or redistribution of solutes during solidificationis closely linked to dendrite arm spacing interdendriticporosity and the amount and distribution of eutectic phases

Themechanism ofmicrosegregation during solidificationof aluminum alloys has received considerable attention butmicrosegregation during solidification of magnesium alloyshas not been systematically studied To understand theinfluence of cooling rate on microsegregation of magnesiumalloys this work aims to carry out an experimental investiga-tion using wedge cast samples of AZ91D AM60B and AE44alloys By applying thewedge casting solidification techniqueit is possible to produce a range of cooling rates in one casting

2 Literature Data

Very few experimental works [7ndash10] regarding the microseg-regation analysis of magnesium alloys were found in theliterature In contrary several studies [11ndash20] were carriedout to investigate the solidification behavior of magnesium-based alloys Although the prime focus of these studieswas not on microsegregation analysis valuable informationregarding elemental composition at different cooling ratesand conditions could be obtained from them Mirkovicand Schmid-Fetzer [8 9] studied the microsegregation ofAZ31 and AM50 alloys applying directional solidificationtechnique They reported that the segregation behavior ofmanganese is opposite compared to both aluminum andzinc This can be explained by understanding the ternaryMg-Al-Mn system where the Mn forms a peritectic systemPeritectic systems are known to show reversed segregationZhang et al [10] studied the microsegregation in direc-tionally solidified Mg-4Al binary alloy They determinedmicrosegregation in specimens directionally solidified withcooling rates ranging from 006 to 08 Ks They reportedthat the concentration profile of Al at high growth rate orhigher cooling rate is closer to the Scheil model Zheng etal [7] investigated the microsegregation pattern of Mg-4Al-4Ca alloy under different growth rates using the directionalsolidification techniqueThey suggested that the Scheilmodelcan be used in microstructure simulation of this alloy asthe microsegregation of the alloying elements (Al and Ca)predicted by this model agreed reasonably well with theEPMAmeasurements

Wei and Warren [21] carried out microstructural char-acterization of several magnesium alloys in the AM seriesin as-cast condition They performed quantitative analysis ofthe Al segregation in the die cast alloys by examining thinfoil specimens in the TEM Compositional measurementsacross an 120572-Mg grain in AM50A at intervals of 180 nmwere performed using X-ray energy dispersive spectrometry(EDS) in the TEM along a straight line They found that theAl composition in the interior ofMg grain was approximately15 wt which increased to 30 wt in the area adjacent tothe grain boundaries They repeated the same procedure fora thin foil sample of die cast AM60A at intervals of 600 nmThe Al content varied from 2wt in the grain interior toapproximately 4wt in the Al-rich grain boundary region

The width of the high Al region was about 2-3mmThey alsoreported that owing to the low Al content no 120573-Al

12Mg17

formed in AM20 but there was intergranular Al segregationBarbagallo et al [19] determined the variation of the

alloying element contents through the grain boundaries ofan HPDC AM60 alloy by means of EPMA line scanningand reported that the Al concentration varied from 25 wtin the bulk 120572-Mg core to 10wt in the boundary regionIt is to be noted that for the same alloy AM60 Wei andWarren [21] and Barbagallo et al [19] reported differentamount of Al content in the grain boundary region and thisis due to the fact that the casting conditions of the sampleswere different Han et al [22] reported that for permanentmold casting of AZ91D alloy in the dendritic center thealuminum concentration is 26 wt but it is 117 wt atthe dendrite edge about 45 times higher than that in thedendrite center Zhang et al [23] conducted experimentsto compare the amount of microsegregation in permanentmold cast and die-cast AZ91 alloys They reported that theaverage concentration of Al and Zn is lower in the diecasting matrix than in the permanent mold casting matrixAverage concentration of Al is 33 wt and for Zn it is033 wt in permanent mold casting and 3wt Al and022wt Zn in die-cast matrix which means the amount ofsegregationwas higher for comparatively faster cooling Ditzeand Schwerdtfeger [24] reported on strip casting of AZ91alloy that the aluminum content increased from 1wt at thecenter of the dendrite arms where solidification had startedto about 25 wt between the arms where solidificationhad ended Guo et al [25] reported that in AZ80 alloy theregions close to the 120573-Mg

17Al12

eutectic phase have higheraluminum contents and that the maximum concentration inthe dendritic interstice varied between 66 wt and 79 wtThey also reported that applying electromagnetic vibrationon the billet they could increase the value of minimum Alconcentration up to 35 wt from 25 wt which is theminimum concentration of Al in the 120572-Mg matrix in thecenter of a conventional die-cast billet This means that theycould reduce the amount of microsegregation by agitatingthe liquid Table 1 summarizes the available data from theliterature

Segregation takes place due to unequal solute diffusionrates in the solid and the liquid phases of the solventmaterial As a result the phases that solidify in the laterstages of the solidification process such as 120573-Mg

17Al12 are

placed between dendrite arms Gungor [26] reported that theextent of microsegregation in an alloy could be determinedexperimentally by measuring one of the following amount ofnonequilibrium eutectic amount of nonequilibrium secondphase minimum solid composition ratio of minimum andmaximum composition of the primary phase and com-position versus fraction solid profile Experimental tech-niques to investigate the extent of microsegregation includequantitative metallography (point count areal and linealmeasurements) X-ray diffraction analysis [27] and electronmicroprobe measurements

Of the techniques available the most widely used onefor characterizing microsegregation is the random samplingapproach developed by Flemings et al [28] commonly






120590119898=1

1198991198620

119899

sum119894=1

1003816100381610038161003816119862119894 minus 11986201003816100381610038161003816 (1)




0is









119878would be the


119870 =119862lowast119878

119862lowast119871

(2)





119862119878119891119878+ 119862119871119891119871= 1198620 (3)

Here 119891119878and 119891



119862119878=119870 sdot 1198620

(1 minus 119891119878) + 119870 sdot 119891

119878

(4)


119878is solute





119878= 1198620[44]



119862119878= 119870 sdot 119862

0(1 minus 119891

119878)119870minus1

(5)



119862119878= 119870119862

0[1 minus (1 minus 2120572119870)119891

119878](119870minus1)(1minus2120572119870)

(6)

where

120572 =4119863119878119905119891

1205822 (7)


119891is the





4 Methodology









12m

m

18m

m24

mm 37

mm 50

mm 68

mm

(a)


Location 3

Location 4

Location 5

Location 634mm

25mm

185mm

12mm9mm6mm

(b)







0102030

400450500550600650

0

10

20

30

6 10 14 18 22 26 30Time (s)

6 10 14 18 22 26 30Time (s)

6 10 14 18 22 26 30Time (s)

Liquidus

Solidus

d2Tdt2

)∘ C2

sminus2

Tem

pera

ture

(∘C)

dTdt (

(

)C

sminus1



















1 1011 1613 6052 1132 1655 7793 1141 16 7264 1015 1187 5845 808 817 3016 518 502 149







ofAZ9

1DA

M60B

andAE4

4alloys

andtheird

etailsin

locatio

ns1and

6Th

epicturesw

eretaken

atmagnificationof

100X

Allo

yLo

catio

nDetails

Edge

ofthew

edge

Colum

nartoequiaxed

transition

Centero

fthe

wedge

AZ9

1D

1

100120583

m

6

AM60B

1 6

AE4

4

1 6


120572-Mg matrix


120573-Mg17Al12

50120583m

Al8Mn5

(a)

120573-Mg17Al12

120572-Mg matrix

50120583m

Mn-rich phase

(b)

120572-Mg matrix

Al3REAl11RE3

50120583m

(c)






17Al12
















17Al12


17Al12






(a)


(b)


(c)





119898)



0

5

10

15

20

25

30

0 10 20 30 40 50 60 70

Wedge locationD

endr

ite ar

m sp

acin

g (120583

m)


1 2 3 4 5 6

(a)

0

5

10

15

20

25

30

35

0 10 20 30 40 50 60 70

Wedge location

Den

drite

arm

spac

ing

(120583m)


1 2 3 4 5 6

(b)

0

10

20

30

40

50

60

0 20 40 60

Wedge location

Den

drite

arm

spac

ing

(120583m)


1 2 3 4 5 6

(c)


C

E

(a)

C

(b)



0

5

10

15

20

25

30

35

60 70 80 90 100

AZ91D

Zn

AlMn

(wt

)

Magnesium (wt)

(a)

0

5

10

15

20

25

30

70 80 90 100

AM60B

Mn

(wt

)

Magnesium (wt)

Al

(b)

(wt

)

Magnesium (wt)

0

1

2

3

4

5

6

7

8

80 85 90 95 100

AE44

AlLa

CeNd

(c)







0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AZ91D-location 1

(a)

0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AZ91D-location 6

(b)

0

04

08

12

16

2

0 02 04 06 08 1

Zn (w

t)

Fraction solid

(c)

0

05

1

15

2

25

3

0 02 04 06 08 1

Zn (w

t)

Fraction solid

(d)





119878) using this




119878and 119891









0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AM60B-location 1

(a)

0

5

10

15

20

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AM60B-location 6

(b)

0

01

02

03

04

05

0 02 04 06 08 1

Mn

(wt

)

Fraction solid

(c)

0

01

02

03

04

05

0 02 04 06 08 1

Mn

(wt

)

Fraction solid

(d)




17Al12



17Al12

is considered






0

2

4

6

8

10

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AE44-location 1

(a)

0

2

4

6

8

10

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AE44-location 6

(b)

0

2

4

6

8

10

0 02 04 06 08 1

Ce (

wt

)

Fraction solid

(c)

0

2

4

6

0 02 04 06 08 1

Ce (

wt

)

Fraction solid

(d)

0

1

2

3

4

5

0 02 04 06 08 1

La (w

t)

Fraction solid

(e)

0

1

2

3

0 02 04 06 08 1

La (w

t)

Fraction solid

(f)
















1 75 55 34 16 30 2082 76 58 40 16 24 2103 8 65 50 21 22 1784 10 71 40 21 12 1325 7 65 27 19 12 926 66 45 20 17 8 86




119898 for a change






1 363 242 256 223 115 3442 357 247 225 254 121 3273 354 249 219 261 130 3044 290 303 189 301 106 3735 312 282 205 278 107 3696 301 293 184 310 090 439

0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

Eutectic129 wt



03

04

05

06

07

0 10 20 30 40 50 60 70

Wedge location


AZ91DAM60BAE44

Segr

egat

ion

devi

atio

n(120590

m)

1 2 3 4 5





6 Summary


17Al12











Acknowledgment


References



























































CeramicsJournal of










Journal of


Journal of


Volume 2014




CoatingsJournal of

Advances in









Volume 2014

MaterialsJournal of

Nano

materials








120590119898=1

1198991198620

119899

sum119894=1

1003816100381610038161003816119862119894 minus 11986201003816100381610038161003816 (1)




0is









119878would be the


119870 =119862lowast119878

119862lowast119871

(2)





119862119878119891119878+ 119862119871119891119871= 1198620 (3)

Here 119891119878and 119891



119862119878=119870 sdot 1198620

(1 minus 119891119878) + 119870 sdot 119891

119878

(4)


119878is solute





119878= 1198620[44]



119862119878= 119870 sdot 119862

0(1 minus 119891

119878)119870minus1

(5)



119862119878= 119870119862

0[1 minus (1 minus 2120572119870)119891

119878](119870minus1)(1minus2120572119870)

(6)

where

120572 =4119863119878119905119891

1205822 (7)


119891is the





4 Methodology









12m

m

18m

m24

mm 37

mm 50

mm 68

mm

(a)


Location 3

Location 4

Location 5

Location 634mm

25mm

185mm

12mm9mm6mm

(b)







0102030

400450500550600650

0

10

20

30

6 10 14 18 22 26 30Time (s)

6 10 14 18 22 26 30Time (s)

6 10 14 18 22 26 30Time (s)

Liquidus

Solidus

d2Tdt2

)∘ C2

sminus2

Tem

pera

ture

(∘C)

dTdt (

(

)C

sminus1



















1 1011 1613 6052 1132 1655 7793 1141 16 7264 1015 1187 5845 808 817 3016 518 502 149







ofAZ9

1DA

M60B

andAE4

4alloys

andtheird

etailsin

locatio

ns1and

6Th

epicturesw

eretaken

atmagnificationof

100X

Allo

yLo

catio

nDetails

Edge

ofthew

edge

Colum

nartoequiaxed

transition

Centero

fthe

wedge

AZ9

1D

1

100120583

m

6

AM60B

1 6

AE4

4

1 6


120572-Mg matrix


120573-Mg17Al12

50120583m

Al8Mn5

(a)

120573-Mg17Al12

120572-Mg matrix

50120583m

Mn-rich phase

(b)

120572-Mg matrix

Al3REAl11RE3

50120583m

(c)






17Al12
















17Al12


17Al12






(a)


(b)


(c)





119898)



0

5

10

15

20

25

30

0 10 20 30 40 50 60 70

Wedge locationD

endr

ite ar

m sp

acin

g (120583

m)


1 2 3 4 5 6

(a)

0

5

10

15

20

25

30

35

0 10 20 30 40 50 60 70

Wedge location

Den

drite

arm

spac

ing

(120583m)


1 2 3 4 5 6

(b)

0

10

20

30

40

50

60

0 20 40 60

Wedge location

Den

drite

arm

spac

ing

(120583m)


1 2 3 4 5 6

(c)


C

E

(a)

C

(b)



0

5

10

15

20

25

30

35

60 70 80 90 100

AZ91D

Zn

AlMn

(wt

)

Magnesium (wt)

(a)

0

5

10

15

20

25

30

70 80 90 100

AM60B

Mn

(wt

)

Magnesium (wt)

Al

(b)

(wt

)

Magnesium (wt)

0

1

2

3

4

5

6

7

8

80 85 90 95 100

AE44

AlLa

CeNd

(c)







0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AZ91D-location 1

(a)

0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AZ91D-location 6

(b)

0

04

08

12

16

2

0 02 04 06 08 1

Zn (w

t)

Fraction solid

(c)

0

05

1

15

2

25

3

0 02 04 06 08 1

Zn (w

t)

Fraction solid

(d)





119878) using this




119878and 119891









0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AM60B-location 1

(a)

0

5

10

15

20

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AM60B-location 6

(b)

0

01

02

03

04

05

0 02 04 06 08 1

Mn

(wt

)

Fraction solid

(c)

0

01

02

03

04

05

0 02 04 06 08 1

Mn

(wt

)

Fraction solid

(d)




17Al12



17Al12

is considered






0

2

4

6

8

10

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AE44-location 1

(a)

0

2

4

6

8

10

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AE44-location 6

(b)

0

2

4

6

8

10

0 02 04 06 08 1

Ce (

wt

)

Fraction solid

(c)

0

2

4

6

0 02 04 06 08 1

Ce (

wt

)

Fraction solid

(d)

0

1

2

3

4

5

0 02 04 06 08 1

La (w

t)

Fraction solid

(e)

0

1

2

3

0 02 04 06 08 1

La (w

t)

Fraction solid

(f)
















1 75 55 34 16 30 2082 76 58 40 16 24 2103 8 65 50 21 22 1784 10 71 40 21 12 1325 7 65 27 19 12 926 66 45 20 17 8 86




119898 for a change






1 363 242 256 223 115 3442 357 247 225 254 121 3273 354 249 219 261 130 3044 290 303 189 301 106 3735 312 282 205 278 107 3696 301 293 184 310 090 439

0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

Eutectic129 wt



03

04

05

06

07

0 10 20 30 40 50 60 70

Wedge location


AZ91DAM60BAE44

Segr

egat

ion

devi

atio

n(120590

m)

1 2 3 4 5





6 Summary


17Al12











Acknowledgment


References



























































CeramicsJournal of










Journal of


Journal of


Volume 2014




CoatingsJournal of

Advances in









Volume 2014

MaterialsJournal of

Nano

materials






119862119878119891119878+ 119862119871119891119871= 1198620 (3)

Here 119891119878and 119891



119862119878=119870 sdot 1198620

(1 minus 119891119878) + 119870 sdot 119891

119878

(4)


119878is solute





119878= 1198620[44]



119862119878= 119870 sdot 119862

0(1 minus 119891

119878)119870minus1

(5)



119862119878= 119870119862

0[1 minus (1 minus 2120572119870)119891

119878](119870minus1)(1minus2120572119870)

(6)

where

120572 =4119863119878119905119891

1205822 (7)


119891is the





4 Methodology









12m

m

18m

m24

mm 37

mm 50

mm 68

mm

(a)


Location 3

Location 4

Location 5

Location 634mm

25mm

185mm

12mm9mm6mm

(b)







0102030

400450500550600650

0

10

20

30

6 10 14 18 22 26 30Time (s)

6 10 14 18 22 26 30Time (s)

6 10 14 18 22 26 30Time (s)

Liquidus

Solidus

d2Tdt2

)∘ C2

sminus2

Tem

pera

ture

(∘C)

dTdt (

(

)C

sminus1



















1 1011 1613 6052 1132 1655 7793 1141 16 7264 1015 1187 5845 808 817 3016 518 502 149







ofAZ9

1DA

M60B

andAE4

4alloys

andtheird

etailsin

locatio

ns1and

6Th

epicturesw

eretaken

atmagnificationof

100X

Allo

yLo

catio

nDetails

Edge

ofthew

edge

Colum

nartoequiaxed

transition

Centero

fthe

wedge

AZ9

1D

1

100120583

m

6

AM60B

1 6

AE4

4

1 6


120572-Mg matrix


120573-Mg17Al12

50120583m

Al8Mn5

(a)

120573-Mg17Al12

120572-Mg matrix

50120583m

Mn-rich phase

(b)

120572-Mg matrix

Al3REAl11RE3

50120583m

(c)






17Al12
















17Al12


17Al12






(a)


(b)


(c)





119898)



0

5

10

15

20

25

30

0 10 20 30 40 50 60 70

Wedge locationD

endr

ite ar

m sp

acin

g (120583

m)


1 2 3 4 5 6

(a)

0

5

10

15

20

25

30

35

0 10 20 30 40 50 60 70

Wedge location

Den

drite

arm

spac

ing

(120583m)


1 2 3 4 5 6

(b)

0

10

20

30

40

50

60

0 20 40 60

Wedge location

Den

drite

arm

spac

ing

(120583m)


1 2 3 4 5 6

(c)


C

E

(a)

C

(b)



0

5

10

15

20

25

30

35

60 70 80 90 100

AZ91D

Zn

AlMn

(wt

)

Magnesium (wt)

(a)

0

5

10

15

20

25

30

70 80 90 100

AM60B

Mn

(wt

)

Magnesium (wt)

Al

(b)

(wt

)

Magnesium (wt)

0

1

2

3

4

5

6

7

8

80 85 90 95 100

AE44

AlLa

CeNd

(c)







0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AZ91D-location 1

(a)

0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AZ91D-location 6

(b)

0

04

08

12

16

2

0 02 04 06 08 1

Zn (w

t)

Fraction solid

(c)

0

05

1

15

2

25

3

0 02 04 06 08 1

Zn (w

t)

Fraction solid

(d)





119878) using this




119878and 119891









0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AM60B-location 1

(a)

0

5

10

15

20

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AM60B-location 6

(b)

0

01

02

03

04

05

0 02 04 06 08 1

Mn

(wt

)

Fraction solid

(c)

0

01

02

03

04

05

0 02 04 06 08 1

Mn

(wt

)

Fraction solid

(d)




17Al12



17Al12

is considered






0

2

4

6

8

10

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AE44-location 1

(a)

0

2

4

6

8

10

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AE44-location 6

(b)

0

2

4

6

8

10

0 02 04 06 08 1

Ce (

wt

)

Fraction solid

(c)

0

2

4

6

0 02 04 06 08 1

Ce (

wt

)

Fraction solid

(d)

0

1

2

3

4

5

0 02 04 06 08 1

La (w

t)

Fraction solid

(e)

0

1

2

3

0 02 04 06 08 1

La (w

t)

Fraction solid

(f)
















1 75 55 34 16 30 2082 76 58 40 16 24 2103 8 65 50 21 22 1784 10 71 40 21 12 1325 7 65 27 19 12 926 66 45 20 17 8 86




119898 for a change






1 363 242 256 223 115 3442 357 247 225 254 121 3273 354 249 219 261 130 3044 290 303 189 301 106 3735 312 282 205 278 107 3696 301 293 184 310 090 439

0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

Eutectic129 wt



03

04

05

06

07

0 10 20 30 40 50 60 70

Wedge location


AZ91DAM60BAE44

Segr

egat

ion

devi

atio

n(120590

m)

1 2 3 4 5





6 Summary


17Al12











Acknowledgment


References



























































CeramicsJournal of










Journal of


Journal of


Volume 2014




CoatingsJournal of

Advances in









Volume 2014

MaterialsJournal of

Nano

materials




12m

m

18m

m24

mm 37

mm 50

mm 68

mm

(a)


Location 3

Location 4

Location 5

Location 634mm

25mm

185mm

12mm9mm6mm

(b)







0102030

400450500550600650

0

10

20

30

6 10 14 18 22 26 30Time (s)

6 10 14 18 22 26 30Time (s)

6 10 14 18 22 26 30Time (s)

Liquidus

Solidus

d2Tdt2

)∘ C2

sminus2

Tem

pera

ture

(∘C)

dTdt (

(

)C

sminus1



















1 1011 1613 6052 1132 1655 7793 1141 16 7264 1015 1187 5845 808 817 3016 518 502 149







ofAZ9

1DA

M60B

andAE4

4alloys

andtheird

etailsin

locatio

ns1and

6Th

epicturesw

eretaken

atmagnificationof

100X

Allo

yLo

catio

nDetails

Edge

ofthew

edge

Colum

nartoequiaxed

transition

Centero

fthe

wedge

AZ9

1D

1

100120583

m

6

AM60B

1 6

AE4

4

1 6


120572-Mg matrix


120573-Mg17Al12

50120583m

Al8Mn5

(a)

120573-Mg17Al12

120572-Mg matrix

50120583m

Mn-rich phase

(b)

120572-Mg matrix

Al3REAl11RE3

50120583m

(c)






17Al12
















17Al12


17Al12






(a)


(b)


(c)





119898)



0

5

10

15

20

25

30

0 10 20 30 40 50 60 70

Wedge locationD

endr

ite ar

m sp

acin

g (120583

m)


1 2 3 4 5 6

(a)

0

5

10

15

20

25

30

35

0 10 20 30 40 50 60 70

Wedge location

Den

drite

arm

spac

ing

(120583m)


1 2 3 4 5 6

(b)

0

10

20

30

40

50

60

0 20 40 60

Wedge location

Den

drite

arm

spac

ing

(120583m)


1 2 3 4 5 6

(c)


C

E

(a)

C

(b)



0

5

10

15

20

25

30

35

60 70 80 90 100

AZ91D

Zn

AlMn

(wt

)

Magnesium (wt)

(a)

0

5

10

15

20

25

30

70 80 90 100

AM60B

Mn

(wt

)

Magnesium (wt)

Al

(b)

(wt

)

Magnesium (wt)

0

1

2

3

4

5

6

7

8

80 85 90 95 100

AE44

AlLa

CeNd

(c)







0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AZ91D-location 1

(a)

0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AZ91D-location 6

(b)

0

04

08

12

16

2

0 02 04 06 08 1

Zn (w

t)

Fraction solid

(c)

0

05

1

15

2

25

3

0 02 04 06 08 1

Zn (w

t)

Fraction solid

(d)





119878) using this




119878and 119891









0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AM60B-location 1

(a)

0

5

10

15

20

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AM60B-location 6

(b)

0

01

02

03

04

05

0 02 04 06 08 1

Mn

(wt

)

Fraction solid

(c)

0

01

02

03

04

05

0 02 04 06 08 1

Mn

(wt

)

Fraction solid

(d)




17Al12



17Al12

is considered






0

2

4

6

8

10

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AE44-location 1

(a)

0

2

4

6

8

10

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AE44-location 6

(b)

0

2

4

6

8

10

0 02 04 06 08 1

Ce (

wt

)

Fraction solid

(c)

0

2

4

6

0 02 04 06 08 1

Ce (

wt

)

Fraction solid

(d)

0

1

2

3

4

5

0 02 04 06 08 1

La (w

t)

Fraction solid

(e)

0

1

2

3

0 02 04 06 08 1

La (w

t)

Fraction solid

(f)
















1 75 55 34 16 30 2082 76 58 40 16 24 2103 8 65 50 21 22 1784 10 71 40 21 12 1325 7 65 27 19 12 926 66 45 20 17 8 86




119898 for a change






1 363 242 256 223 115 3442 357 247 225 254 121 3273 354 249 219 261 130 3044 290 303 189 301 106 3735 312 282 205 278 107 3696 301 293 184 310 090 439

0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

Eutectic129 wt



03

04

05

06

07

0 10 20 30 40 50 60 70

Wedge location


AZ91DAM60BAE44

Segr

egat

ion

devi

atio

n(120590

m)

1 2 3 4 5





6 Summary


17Al12











Acknowledgment


References



























































CeramicsJournal of










Journal of


Journal of


Volume 2014




CoatingsJournal of

Advances in









Volume 2014

MaterialsJournal of

Nano

materials
















1 1011 1613 6052 1132 1655 7793 1141 16 7264 1015 1187 5845 808 817 3016 518 502 149







ofAZ9

1DA

M60B

andAE4

4alloys

andtheird

etailsin

locatio

ns1and

6Th

epicturesw

eretaken

atmagnificationof

100X

Allo

yLo

catio

nDetails

Edge

ofthew

edge

Colum

nartoequiaxed

transition

Centero

fthe

wedge

AZ9

1D

1

100120583

m

6

AM60B

1 6

AE4

4

1 6


120572-Mg matrix


120573-Mg17Al12

50120583m

Al8Mn5

(a)

120573-Mg17Al12

120572-Mg matrix

50120583m

Mn-rich phase

(b)

120572-Mg matrix

Al3REAl11RE3

50120583m

(c)






17Al12
















17Al12


17Al12






(a)


(b)


(c)





119898)



0

5

10

15

20

25

30

0 10 20 30 40 50 60 70

Wedge locationD

endr

ite ar

m sp

acin

g (120583

m)


1 2 3 4 5 6

(a)

0

5

10

15

20

25

30

35

0 10 20 30 40 50 60 70

Wedge location

Den

drite

arm

spac

ing

(120583m)


1 2 3 4 5 6

(b)

0

10

20

30

40

50

60

0 20 40 60

Wedge location

Den

drite

arm

spac

ing

(120583m)


1 2 3 4 5 6

(c)


C

E

(a)

C

(b)



0

5

10

15

20

25

30

35

60 70 80 90 100

AZ91D

Zn

AlMn

(wt

)

Magnesium (wt)

(a)

0

5

10

15

20

25

30

70 80 90 100

AM60B

Mn

(wt

)

Magnesium (wt)

Al

(b)

(wt

)

Magnesium (wt)

0

1

2

3

4

5

6

7

8

80 85 90 95 100

AE44

AlLa

CeNd

(c)







0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AZ91D-location 1

(a)

0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AZ91D-location 6

(b)

0

04

08

12

16

2

0 02 04 06 08 1

Zn (w

t)

Fraction solid

(c)

0

05

1

15

2

25

3

0 02 04 06 08 1

Zn (w

t)

Fraction solid

(d)





119878) using this




119878and 119891









0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AM60B-location 1

(a)

0

5

10

15

20

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AM60B-location 6

(b)

0

01

02

03

04

05

0 02 04 06 08 1

Mn

(wt

)

Fraction solid

(c)

0

01

02

03

04

05

0 02 04 06 08 1

Mn

(wt

)

Fraction solid

(d)




17Al12



17Al12

is considered






0

2

4

6

8

10

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AE44-location 1

(a)

0

2

4

6

8

10

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AE44-location 6

(b)

0

2

4

6

8

10

0 02 04 06 08 1

Ce (

wt

)

Fraction solid

(c)

0

2

4

6

0 02 04 06 08 1

Ce (

wt

)

Fraction solid

(d)

0

1

2

3

4

5

0 02 04 06 08 1

La (w

t)

Fraction solid

(e)

0

1

2

3

0 02 04 06 08 1

La (w

t)

Fraction solid

(f)
















1 75 55 34 16 30 2082 76 58 40 16 24 2103 8 65 50 21 22 1784 10 71 40 21 12 1325 7 65 27 19 12 926 66 45 20 17 8 86




119898 for a change






1 363 242 256 223 115 3442 357 247 225 254 121 3273 354 249 219 261 130 3044 290 303 189 301 106 3735 312 282 205 278 107 3696 301 293 184 310 090 439

0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

Eutectic129 wt



03

04

05

06

07

0 10 20 30 40 50 60 70

Wedge location


AZ91DAM60BAE44

Segr

egat

ion

devi

atio

n(120590

m)

1 2 3 4 5





6 Summary


17Al12











Acknowledgment


References



























































CeramicsJournal of










Journal of


Journal of


Volume 2014




CoatingsJournal of

Advances in









Volume 2014

MaterialsJournal of

Nano

materials





ofAZ9

1DA

M60B

andAE4

4alloys

andtheird

etailsin

locatio

ns1and

6Th

epicturesw

eretaken

atmagnificationof

100X

Allo

yLo

catio

nDetails

Edge

ofthew

edge

Colum

nartoequiaxed

transition

Centero

fthe

wedge

AZ9

1D

1

100120583

m

6

AM60B

1 6

AE4

4

1 6


120572-Mg matrix


120573-Mg17Al12

50120583m

Al8Mn5

(a)

120573-Mg17Al12

120572-Mg matrix

50120583m

Mn-rich phase

(b)

120572-Mg matrix

Al3REAl11RE3

50120583m

(c)






17Al12
















17Al12


17Al12






(a)


(b)


(c)





119898)



0

5

10

15

20

25

30

0 10 20 30 40 50 60 70

Wedge locationD

endr

ite ar

m sp

acin

g (120583

m)


1 2 3 4 5 6

(a)

0

5

10

15

20

25

30

35

0 10 20 30 40 50 60 70

Wedge location

Den

drite

arm

spac

ing

(120583m)


1 2 3 4 5 6

(b)

0

10

20

30

40

50

60

0 20 40 60

Wedge location

Den

drite

arm

spac

ing

(120583m)


1 2 3 4 5 6

(c)


C

E

(a)

C

(b)



0

5

10

15

20

25

30

35

60 70 80 90 100

AZ91D

Zn

AlMn

(wt

)

Magnesium (wt)

(a)

0

5

10

15

20

25

30

70 80 90 100

AM60B

Mn

(wt

)

Magnesium (wt)

Al

(b)

(wt

)

Magnesium (wt)

0

1

2

3

4

5

6

7

8

80 85 90 95 100

AE44

AlLa

CeNd

(c)







0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AZ91D-location 1

(a)

0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AZ91D-location 6

(b)

0

04

08

12

16

2

0 02 04 06 08 1

Zn (w

t)

Fraction solid

(c)

0

05

1

15

2

25

3

0 02 04 06 08 1

Zn (w

t)

Fraction solid

(d)





119878) using this




119878and 119891









0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AM60B-location 1

(a)

0

5

10

15

20

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AM60B-location 6

(b)

0

01

02

03

04

05

0 02 04 06 08 1

Mn

(wt

)

Fraction solid

(c)

0

01

02

03

04

05

0 02 04 06 08 1

Mn

(wt

)

Fraction solid

(d)




17Al12



17Al12

is considered






0

2

4

6

8

10

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AE44-location 1

(a)

0

2

4

6

8

10

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AE44-location 6

(b)

0

2

4

6

8

10

0 02 04 06 08 1

Ce (

wt

)

Fraction solid

(c)

0

2

4

6

0 02 04 06 08 1

Ce (

wt

)

Fraction solid

(d)

0

1

2

3

4

5

0 02 04 06 08 1

La (w

t)

Fraction solid

(e)

0

1

2

3

0 02 04 06 08 1

La (w

t)

Fraction solid

(f)
















1 75 55 34 16 30 2082 76 58 40 16 24 2103 8 65 50 21 22 1784 10 71 40 21 12 1325 7 65 27 19 12 926 66 45 20 17 8 86




119898 for a change






1 363 242 256 223 115 3442 357 247 225 254 121 3273 354 249 219 261 130 3044 290 303 189 301 106 3735 312 282 205 278 107 3696 301 293 184 310 090 439

0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

Eutectic129 wt



03

04

05

06

07

0 10 20 30 40 50 60 70

Wedge location


AZ91DAM60BAE44

Segr

egat

ion

devi

atio

n(120590

m)

1 2 3 4 5





6 Summary


17Al12











Acknowledgment


References



























































CeramicsJournal of










Journal of


Journal of


Volume 2014




CoatingsJournal of

Advances in









Volume 2014

MaterialsJournal of

Nano

materials




120572-Mg matrix


120573-Mg17Al12

50120583m

Al8Mn5

(a)

120573-Mg17Al12

120572-Mg matrix

50120583m

Mn-rich phase

(b)

120572-Mg matrix

Al3REAl11RE3

50120583m

(c)






17Al12
















17Al12


17Al12






(a)


(b)


(c)





119898)



0

5

10

15

20

25

30

0 10 20 30 40 50 60 70

Wedge locationD

endr

ite ar

m sp

acin

g (120583

m)


1 2 3 4 5 6

(a)

0

5

10

15

20

25

30

35

0 10 20 30 40 50 60 70

Wedge location

Den

drite

arm

spac

ing

(120583m)


1 2 3 4 5 6

(b)

0

10

20

30

40

50

60

0 20 40 60

Wedge location

Den

drite

arm

spac

ing

(120583m)


1 2 3 4 5 6

(c)


C

E

(a)

C

(b)



0

5

10

15

20

25

30

35

60 70 80 90 100

AZ91D

Zn

AlMn

(wt

)

Magnesium (wt)

(a)

0

5

10

15

20

25

30

70 80 90 100

AM60B

Mn

(wt

)

Magnesium (wt)

Al

(b)

(wt

)

Magnesium (wt)

0

1

2

3

4

5

6

7

8

80 85 90 95 100

AE44

AlLa

CeNd

(c)







0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AZ91D-location 1

(a)

0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AZ91D-location 6

(b)

0

04

08

12

16

2

0 02 04 06 08 1

Zn (w

t)

Fraction solid

(c)

0

05

1

15

2

25

3

0 02 04 06 08 1

Zn (w

t)

Fraction solid

(d)





119878) using this




119878and 119891









0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AM60B-location 1

(a)

0

5

10

15

20

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AM60B-location 6

(b)

0

01

02

03

04

05

0 02 04 06 08 1

Mn

(wt

)

Fraction solid

(c)

0

01

02

03

04

05

0 02 04 06 08 1

Mn

(wt

)

Fraction solid

(d)




17Al12



17Al12

is considered






0

2

4

6

8

10

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AE44-location 1

(a)

0

2

4

6

8

10

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AE44-location 6

(b)

0

2

4

6

8

10

0 02 04 06 08 1

Ce (

wt

)

Fraction solid

(c)

0

2

4

6

0 02 04 06 08 1

Ce (

wt

)

Fraction solid

(d)

0

1

2

3

4

5

0 02 04 06 08 1

La (w

t)

Fraction solid

(e)

0

1

2

3

0 02 04 06 08 1

La (w

t)

Fraction solid

(f)
















1 75 55 34 16 30 2082 76 58 40 16 24 2103 8 65 50 21 22 1784 10 71 40 21 12 1325 7 65 27 19 12 926 66 45 20 17 8 86




119898 for a change






1 363 242 256 223 115 3442 357 247 225 254 121 3273 354 249 219 261 130 3044 290 303 189 301 106 3735 312 282 205 278 107 3696 301 293 184 310 090 439

0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

Eutectic129 wt



03

04

05

06

07

0 10 20 30 40 50 60 70

Wedge location


AZ91DAM60BAE44

Segr

egat

ion

devi

atio

n(120590

m)

1 2 3 4 5





6 Summary


17Al12











Acknowledgment


References



























































CeramicsJournal of










Journal of


Journal of


Volume 2014




CoatingsJournal of

Advances in









Volume 2014

MaterialsJournal of

Nano

materials





(a)


(b)


(c)





119898)



0

5

10

15

20

25

30

0 10 20 30 40 50 60 70

Wedge locationD

endr

ite ar

m sp

acin

g (120583

m)


1 2 3 4 5 6

(a)

0

5

10

15

20

25

30

35

0 10 20 30 40 50 60 70

Wedge location

Den

drite

arm

spac

ing

(120583m)


1 2 3 4 5 6

(b)

0

10

20

30

40

50

60

0 20 40 60

Wedge location

Den

drite

arm

spac

ing

(120583m)


1 2 3 4 5 6

(c)


C

E

(a)

C

(b)



0

5

10

15

20

25

30

35

60 70 80 90 100

AZ91D

Zn

AlMn

(wt

)

Magnesium (wt)

(a)

0

5

10

15

20

25

30

70 80 90 100

AM60B

Mn

(wt

)

Magnesium (wt)

Al

(b)

(wt

)

Magnesium (wt)

0

1

2

3

4

5

6

7

8

80 85 90 95 100

AE44

AlLa

CeNd

(c)







0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AZ91D-location 1

(a)

0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AZ91D-location 6

(b)

0

04

08

12

16

2

0 02 04 06 08 1

Zn (w

t)

Fraction solid

(c)

0

05

1

15

2

25

3

0 02 04 06 08 1

Zn (w

t)

Fraction solid

(d)





119878) using this




119878and 119891









0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AM60B-location 1

(a)

0

5

10

15

20

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AM60B-location 6

(b)

0

01

02

03

04

05

0 02 04 06 08 1

Mn

(wt

)

Fraction solid

(c)

0

01

02

03

04

05

0 02 04 06 08 1

Mn

(wt

)

Fraction solid

(d)




17Al12



17Al12

is considered






0

2

4

6

8

10

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AE44-location 1

(a)

0

2

4

6

8

10

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AE44-location 6

(b)

0

2

4

6

8

10

0 02 04 06 08 1

Ce (

wt

)

Fraction solid

(c)

0

2

4

6

0 02 04 06 08 1

Ce (

wt

)

Fraction solid

(d)

0

1

2

3

4

5

0 02 04 06 08 1

La (w

t)

Fraction solid

(e)

0

1

2

3

0 02 04 06 08 1

La (w

t)

Fraction solid

(f)
















1 75 55 34 16 30 2082 76 58 40 16 24 2103 8 65 50 21 22 1784 10 71 40 21 12 1325 7 65 27 19 12 926 66 45 20 17 8 86




119898 for a change






1 363 242 256 223 115 3442 357 247 225 254 121 3273 354 249 219 261 130 3044 290 303 189 301 106 3735 312 282 205 278 107 3696 301 293 184 310 090 439

0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

Eutectic129 wt



03

04

05

06

07

0 10 20 30 40 50 60 70

Wedge location


AZ91DAM60BAE44

Segr

egat

ion

devi

atio

n(120590

m)

1 2 3 4 5





6 Summary


17Al12











Acknowledgment


References



























































CeramicsJournal of










Journal of


Journal of


Volume 2014




CoatingsJournal of

Advances in









Volume 2014

MaterialsJournal of

Nano

materials




0

5

10

15

20

25

30

0 10 20 30 40 50 60 70

Wedge locationD

endr

ite ar

m sp

acin

g (120583

m)


1 2 3 4 5 6

(a)

0

5

10

15

20

25

30

35

0 10 20 30 40 50 60 70

Wedge location

Den

drite

arm

spac

ing

(120583m)


1 2 3 4 5 6

(b)

0

10

20

30

40

50

60

0 20 40 60

Wedge location

Den

drite

arm

spac

ing

(120583m)


1 2 3 4 5 6

(c)


C

E

(a)

C

(b)



0

5

10

15

20

25

30

35

60 70 80 90 100

AZ91D

Zn

AlMn

(wt

)

Magnesium (wt)

(a)

0

5

10

15

20

25

30

70 80 90 100

AM60B

Mn

(wt

)

Magnesium (wt)

Al

(b)

(wt

)

Magnesium (wt)

0

1

2

3

4

5

6

7

8

80 85 90 95 100

AE44

AlLa

CeNd

(c)







0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AZ91D-location 1

(a)

0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AZ91D-location 6

(b)

0

04

08

12

16

2

0 02 04 06 08 1

Zn (w

t)

Fraction solid

(c)

0

05

1

15

2

25

3

0 02 04 06 08 1

Zn (w

t)

Fraction solid

(d)





119878) using this




119878and 119891









0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AM60B-location 1

(a)

0

5

10

15

20

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AM60B-location 6

(b)

0

01

02

03

04

05

0 02 04 06 08 1

Mn

(wt

)

Fraction solid

(c)

0

01

02

03

04

05

0 02 04 06 08 1

Mn

(wt

)

Fraction solid

(d)




17Al12



17Al12

is considered






0

2

4

6

8

10

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AE44-location 1

(a)

0

2

4

6

8

10

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AE44-location 6

(b)

0

2

4

6

8

10

0 02 04 06 08 1

Ce (

wt

)

Fraction solid

(c)

0

2

4

6

0 02 04 06 08 1

Ce (

wt

)

Fraction solid

(d)

0

1

2

3

4

5

0 02 04 06 08 1

La (w

t)

Fraction solid

(e)

0

1

2

3

0 02 04 06 08 1

La (w

t)

Fraction solid

(f)
















1 75 55 34 16 30 2082 76 58 40 16 24 2103 8 65 50 21 22 1784 10 71 40 21 12 1325 7 65 27 19 12 926 66 45 20 17 8 86




119898 for a change






1 363 242 256 223 115 3442 357 247 225 254 121 3273 354 249 219 261 130 3044 290 303 189 301 106 3735 312 282 205 278 107 3696 301 293 184 310 090 439

0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

Eutectic129 wt



03

04

05

06

07

0 10 20 30 40 50 60 70

Wedge location


AZ91DAM60BAE44

Segr

egat

ion

devi

atio

n(120590

m)

1 2 3 4 5





6 Summary


17Al12











Acknowledgment


References



























































CeramicsJournal of










Journal of


Journal of


Volume 2014




CoatingsJournal of

Advances in









Volume 2014

MaterialsJournal of

Nano

materials




0

5

10

15

20

25

30

35

60 70 80 90 100

AZ91D

Zn

AlMn

(wt

)

Magnesium (wt)

(a)

0

5

10

15

20

25

30

70 80 90 100

AM60B

Mn

(wt

)

Magnesium (wt)

Al

(b)

(wt

)

Magnesium (wt)

0

1

2

3

4

5

6

7

8

80 85 90 95 100

AE44

AlLa

CeNd

(c)







0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AZ91D-location 1

(a)

0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AZ91D-location 6

(b)

0

04

08

12

16

2

0 02 04 06 08 1

Zn (w

t)

Fraction solid

(c)

0

05

1

15

2

25

3

0 02 04 06 08 1

Zn (w

t)

Fraction solid

(d)





119878) using this




119878and 119891









0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AM60B-location 1

(a)

0

5

10

15

20

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AM60B-location 6

(b)

0

01

02

03

04

05

0 02 04 06 08 1

Mn

(wt

)

Fraction solid

(c)

0

01

02

03

04

05

0 02 04 06 08 1

Mn

(wt

)

Fraction solid

(d)




17Al12



17Al12

is considered






0

2

4

6

8

10

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AE44-location 1

(a)

0

2

4

6

8

10

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AE44-location 6

(b)

0

2

4

6

8

10

0 02 04 06 08 1

Ce (

wt

)

Fraction solid

(c)

0

2

4

6

0 02 04 06 08 1

Ce (

wt

)

Fraction solid

(d)

0

1

2

3

4

5

0 02 04 06 08 1

La (w

t)

Fraction solid

(e)

0

1

2

3

0 02 04 06 08 1

La (w

t)

Fraction solid

(f)
















1 75 55 34 16 30 2082 76 58 40 16 24 2103 8 65 50 21 22 1784 10 71 40 21 12 1325 7 65 27 19 12 926 66 45 20 17 8 86




119898 for a change






1 363 242 256 223 115 3442 357 247 225 254 121 3273 354 249 219 261 130 3044 290 303 189 301 106 3735 312 282 205 278 107 3696 301 293 184 310 090 439

0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

Eutectic129 wt



03

04

05

06

07

0 10 20 30 40 50 60 70

Wedge location


AZ91DAM60BAE44

Segr

egat

ion

devi

atio

n(120590

m)

1 2 3 4 5





6 Summary


17Al12











Acknowledgment


References



























































CeramicsJournal of










Journal of


Journal of


Volume 2014




CoatingsJournal of

Advances in









Volume 2014

MaterialsJournal of

Nano

materials




0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AZ91D-location 1

(a)

0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AZ91D-location 6

(b)

0

04

08

12

16

2

0 02 04 06 08 1

Zn (w

t)

Fraction solid

(c)

0

05

1

15

2

25

3

0 02 04 06 08 1

Zn (w

t)

Fraction solid

(d)





119878) using this




119878and 119891









0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AM60B-location 1

(a)

0

5

10

15

20

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AM60B-location 6

(b)

0

01

02

03

04

05

0 02 04 06 08 1

Mn

(wt

)

Fraction solid

(c)

0

01

02

03

04

05

0 02 04 06 08 1

Mn

(wt

)

Fraction solid

(d)




17Al12



17Al12

is considered






0

2

4

6

8

10

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AE44-location 1

(a)

0

2

4

6

8

10

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AE44-location 6

(b)

0

2

4

6

8

10

0 02 04 06 08 1

Ce (

wt

)

Fraction solid

(c)

0

2

4

6

0 02 04 06 08 1

Ce (

wt

)

Fraction solid

(d)

0

1

2

3

4

5

0 02 04 06 08 1

La (w

t)

Fraction solid

(e)

0

1

2

3

0 02 04 06 08 1

La (w

t)

Fraction solid

(f)
















1 75 55 34 16 30 2082 76 58 40 16 24 2103 8 65 50 21 22 1784 10 71 40 21 12 1325 7 65 27 19 12 926 66 45 20 17 8 86




119898 for a change






1 363 242 256 223 115 3442 357 247 225 254 121 3273 354 249 219 261 130 3044 290 303 189 301 106 3735 312 282 205 278 107 3696 301 293 184 310 090 439

0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

Eutectic129 wt



03

04

05

06

07

0 10 20 30 40 50 60 70

Wedge location


AZ91DAM60BAE44

Segr

egat

ion

devi

atio

n(120590

m)

1 2 3 4 5





6 Summary


17Al12











Acknowledgment


References



























































CeramicsJournal of










Journal of


Journal of


Volume 2014




CoatingsJournal of

Advances in









Volume 2014

MaterialsJournal of

Nano

materials




0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AM60B-location 1

(a)

0

5

10

15

20

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AM60B-location 6

(b)

0

01

02

03

04

05

0 02 04 06 08 1

Mn

(wt

)

Fraction solid

(c)

0

01

02

03

04

05

0 02 04 06 08 1

Mn

(wt

)

Fraction solid

(d)




17Al12



17Al12

is considered






0

2

4

6

8

10

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AE44-location 1

(a)

0

2

4

6

8

10

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AE44-location 6

(b)

0

2

4

6

8

10

0 02 04 06 08 1

Ce (

wt

)

Fraction solid

(c)

0

2

4

6

0 02 04 06 08 1

Ce (

wt

)

Fraction solid

(d)

0

1

2

3

4

5

0 02 04 06 08 1

La (w

t)

Fraction solid

(e)

0

1

2

3

0 02 04 06 08 1

La (w

t)

Fraction solid

(f)
















1 75 55 34 16 30 2082 76 58 40 16 24 2103 8 65 50 21 22 1784 10 71 40 21 12 1325 7 65 27 19 12 926 66 45 20 17 8 86




119898 for a change






1 363 242 256 223 115 3442 357 247 225 254 121 3273 354 249 219 261 130 3044 290 303 189 301 106 3735 312 282 205 278 107 3696 301 293 184 310 090 439

0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

Eutectic129 wt



03

04

05

06

07

0 10 20 30 40 50 60 70

Wedge location


AZ91DAM60BAE44

Segr

egat

ion

devi

atio

n(120590

m)

1 2 3 4 5





6 Summary


17Al12











Acknowledgment


References



























































CeramicsJournal of










Journal of


Journal of


Volume 2014




CoatingsJournal of

Advances in









Volume 2014

MaterialsJournal of

Nano

materials




0

2

4

6

8

10

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AE44-location 1

(a)

0

2

4

6

8

10

0 02 04 06 08 1

Al (

wt

)

Fraction solid

AE44-location 6

(b)

0

2

4

6

8

10

0 02 04 06 08 1

Ce (

wt

)

Fraction solid

(c)

0

2

4

6

0 02 04 06 08 1

Ce (

wt

)

Fraction solid

(d)

0

1

2

3

4

5

0 02 04 06 08 1

La (w

t)

Fraction solid

(e)

0

1

2

3

0 02 04 06 08 1

La (w

t)

Fraction solid

(f)
















1 75 55 34 16 30 2082 76 58 40 16 24 2103 8 65 50 21 22 1784 10 71 40 21 12 1325 7 65 27 19 12 926 66 45 20 17 8 86




119898 for a change






1 363 242 256 223 115 3442 357 247 225 254 121 3273 354 249 219 261 130 3044 290 303 189 301 106 3735 312 282 205 278 107 3696 301 293 184 310 090 439

0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

Eutectic129 wt



03

04

05

06

07

0 10 20 30 40 50 60 70

Wedge location


AZ91DAM60BAE44

Segr

egat

ion

devi

atio

n(120590

m)

1 2 3 4 5





6 Summary


17Al12











Acknowledgment


References



























































CeramicsJournal of










Journal of


Journal of


Volume 2014




CoatingsJournal of

Advances in









Volume 2014

MaterialsJournal of

Nano

materials















1 75 55 34 16 30 2082 76 58 40 16 24 2103 8 65 50 21 22 1784 10 71 40 21 12 1325 7 65 27 19 12 926 66 45 20 17 8 86




119898 for a change






1 363 242 256 223 115 3442 357 247 225 254 121 3273 354 249 219 261 130 3044 290 303 189 301 106 3735 312 282 205 278 107 3696 301 293 184 310 090 439

0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

Eutectic129 wt



03

04

05

06

07

0 10 20 30 40 50 60 70

Wedge location


AZ91DAM60BAE44

Segr

egat

ion

devi

atio

n(120590

m)

1 2 3 4 5





6 Summary


17Al12











Acknowledgment


References



























































CeramicsJournal of










Journal of


Journal of


Volume 2014




CoatingsJournal of

Advances in









Volume 2014

MaterialsJournal of

Nano

materials






1 363 242 256 223 115 3442 357 247 225 254 121 3273 354 249 219 261 130 3044 290 303 189 301 106 3735 312 282 205 278 107 3696 301 293 184 310 090 439

0

5

10

15

20

25

30

0 02 04 06 08 1

Al (

wt

)

Fraction solid

Eutectic129 wt



03

04

05

06

07

0 10 20 30 40 50 60 70

Wedge location


AZ91DAM60BAE44

Segr

egat

ion

devi

atio

n(120590

m)

1 2 3 4 5





6 Summary


17Al12











Acknowledgment


References



























































CeramicsJournal of










Journal of


Journal of


Volume 2014




CoatingsJournal of

Advances in









Volume 2014

MaterialsJournal of

Nano

materials







Acknowledgment


References



























































CeramicsJournal of










Journal of


Journal of


Volume 2014




CoatingsJournal of

Advances in









Volume 2014

MaterialsJournal of

Nano

materials


































CeramicsJournal of










Journal of


Journal of


Volume 2014




CoatingsJournal of

Advances in









Volume 2014

MaterialsJournal of

Nano

materials



Influence of Cooling Rate on Microsegregation Behavior of … · 2016-04-20 · Compositional...

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Transcript of Influence of Cooling Rate on Microsegregation Behavior of … · 2016-04-20 · Compositional...