HEAT TREATMENT EFFECT ON MECHANICAL … · limited research work has been reported on AMCs...
Transcript of HEAT TREATMENT EFFECT ON MECHANICAL … · limited research work has been reported on AMCs...
http://www.iaeme.com/IJMET/index.asp 232 [email protected]
International Journal of Mechanical Engineering and Technology (IJMET)
Volume 7, Issue 2, March-April 2016, pp. 232–243, Article ID: IJMET_07_02_025
Available online at
http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=7&IType=2
Journal Impact Factor (2016): 9.2286 (Calculated by GISI) www.jifactor.com
ISSN Print: 0976-6340 and ISSN Online: 0976-6359
© IAEME Publication
HEAT TREATMENT EFFECT ON
MECHANICAL PROPERTIES AND SEM
ANALYSIS OF AL6061/WC/B4C/TI/CR
METAL MATRIX COMPOSITES
Sivakumar.M
Assistant professor, Mechanical Engineering,
Maharaja Institute of technology, Coimbatore, India
Vignesh.M, Sridhar.R, Sri Hari.K, RamaSubramanian.R
Students, Mechanical Engineering,
Maharaja Institute of technology, Coimbatore, India
ABSTRACT
Recent developments in material technology help to find and fabricate new
materials which may replace existing materials for various applications.
Among those, composite materials play a vital role which is combination of
two or more materials with different physical and chemical properties.
Aluminum plays a vital role in the automotive, aerospace and marine
industries this for its strength, less weight, flexibility and cost. The present
study is to cast a metal matrix composite of al 6061 with the selected
reinforcing materials. The reinforcing material used here are titanium (Ti),
tungsten carbide (Wc), boron carbide (B4C) and chromium (Cr) in the form of
particles. The casting is done using the stir casting method and the
mechanical properties and SEM analysis of the hybrid composites are tested
with the ASTM standard’s and are compared with the pure Al6061. The
mechanical properties of the aluminum metal matrix composites such as
impact, tensile and hardness are tested. The tensile specimens hardened using
the annealing and normalizing process and the tests are taken with the
different specimens and these are compared with Al6061.
Key words: Al6061-Ti-B4C, Al6061-Wc-Cr metal matrix composite, tensile
strength, impact, hardness, x-ray diffraction, scanning electron microscopy.
Cite this Article Sivakumar.M, Vignesh.M, Sridhar.R, Sri Hari.K,
RamaSubramanian.R, Study of Process Parameters of Gravity Die Casting
Defects. International Journal of Mechanical Engineering and Technology,
7(2), 2016, pp. 232–243.
http://www.iaeme.com/currentissue.asp?JType=IJMET&VType=7&IType=2
Heat treatment effect on mechanical properties and SEM analysis of
Al6061/Wc/B4C/Ti/Cr metal matrix composites
http://www.iaeme.com/IJMET/index.asp 233 [email protected]
1. INTRODUCTION
These days engineering need modern materials to develop materials for most
compound applications, since aluminum is most commonly used material in the
automotive and aerospace fields the composite metals based on aluminum has
increased. Among the aluminum materials al6061 is widely used due to its corrosion
resistance, stability, and less cost. Due to the need of more strength, thermal
resistance for these applications leads a way to the fabrication of the aluminum metal
matrix composites. Here the al6061 is reinforced with the titanium, boron carbide,
chromium and tungsten carbide materials. Among these materials titanium and
chromium possessed with high strength. Boron carbide and tungsten carbide has the
high thermal resistance. These materials were combined and reinforced with the stir
casting process currently practiced continuously. In general stir casting of MMCs
involves producing a melt of the selected matrix material followed by introducing
reinforcement material into the melt, obtaining a suitable dispersion through stirring.
Its advantages lie in its simplicity, flexibility and applicability to large quantity
production.
2. LITERATURE REVIEW
V. L. Kingston et al [3]- -Aluminum based matrix composites remain the most
explored metal matrix material for the development of MMCs. In the present study,
the effect of Silicon carbide, Boron carbide on Stir cast Aluminum Metal Matrix
Composites is discussed. Graphite is used as a lubricant. Aluminum Metal Matrix
Composites with Silicon carbide and Boron carbide particle reinforcements are
finding increased applications in aerospace, automobile, space, underwater, and
transportation applications. The hybrid metal matrix composite which consists of
aluminum and other constituents such as graphite, silicon carbide and boron carbide
are to be casted in three different compositions varying the boron carbide and silicon
carbide content and are further employed to different testing such as hardness test,
compression test, tensile test, impact test, micro hardness and micro structural
analysis. Conventional stir casting process has been employed for producing
discontinuous particle reinforced metal matrix composites.(with the mixture of Ti, Wc
and Cr).
3. EXPERIMENTAL PROCEDURE
Materials used
The materials used for the fabrication of the composites are titanium, boron carbide,
tungsten carbide and chromium. Each material has its own unique mechanical
properties. We have selected two composition to form two types of MMC. The
compositions are as follows.
i) 1000gAl6061+10%wt Ti+5%wt B4C.
ii) 1000gAl6061+10%wt Wc+3%wt Cr.
The above two compositions are fabricated and their mechanical properties are
compared with that of the pure aluminum. The material selected are described below
with their mechanical properties in a tabular column.
3.1. ALUMINUM
Aluminum is remarkable for the metal's low density and for its ability to resist
corrosion due to the phenomenon of passivation. Commercially pure aluminum has a
Sivakumar.M, Vignesh.M, Sridhar.R, Sri Hari.K, RamaSubramanian.R
http://www.iaeme.com/IJMET/index.asp 234 [email protected]
tensile strength of approximately 120 MPa and can be improved 180 MPa by cold
working. The heat treatable grades can develop a tensile strength of around 570 MPa
and even higher in some alloys. The wear of MMCs depends on the particular wear
conditions, but there are many circumstances where Al based composites have
excellent wear resistance. The coefficient of thermal expansion of aluminum alloys is
affected by the nature of their constituents: example the presence of silicon and
copper reduces expansion while magnesium increases it. The chemical composition of
the Al 6061 is shown in the table below.
Table 1 composition of Al6061.
3.2. BORON CARBIDE
Boron Carbide particulate reinforced aluminum composites possess a unique
combination of high specific strength, high elastic modulus, good wear resistance and
good thermal stability than the corresponding non-reinforced matrix alloy system. A
limited research work has been reported on AMCs reinforced with B4C due to higher
raw material cost and poor wetting. B4C is a robust material having excellent
chemical and thermal stability, high hardness and low density (2.52 g/cm3) and it is
used for manufacturing bullet proof vests, armor tank, etc. Hence, B4C reinforced
aluminum matrix composite has gained more attraction with low cost casting route.
3.3. TITANIUM
Titanium metal is a strong material when reinforced with aluminum composite they
possess heavy strength for the composite. Since the aluminum is lighter and this
titanium composite gives the strength to that of the aluminum composite and increase
the hardness of the material. The tensile strength of the titanium metal is 250 Mpa as
it has a density of 4.56g/cm3 and it is used in the aerospace materials.
3.4. TUNGSTEN CARBIDE
As we know the tungsten carbide is the stronger material, with a melting point of
2830oc and with the highest tensile strength when the material is mixed with the
aluminum the properties of the materials are shared with that of the aluminum and this
will give the composite the high melting point and the tensile strength. As the density
of the material is concerned the density of the material is 15.6g/cm3 with a highest
density of the selected materials so the mixing of the material takes some time but the
mixture will be strong enough than anything due to the high density.
3.5. CHROMIUM
Chromium is the shiniest of all the metals and they are used in the process of making
chrome plating. The car bumpers and other parts are made of chromium for their
shine property but the cost of the material cost them more. But when the metal is
mixed with the aluminum the property of the metal is adapted by the composite and
the composite material can be used in the automotive fields. The melting point of the
material is 1907oc and the young’s modulus of the material is 279 GPa. The density of
the material is 7.19g/cm3.
ELEMENTS Si Cu Mg Fe Mn Al
PERCENTAGE 0.63 0.32 1.08 1.72 0.52 rem
Heat treatment effect on mechanical properties and SEM analysis of
Al6061/Wc/B4C/Ti/Cr metal matrix composites
http://www.iaeme.com/IJMET/index.asp 235 [email protected]
Table 2 Mechanical properties of the materials
3.6. Fabrication method
Aluminum alloys was melted in a graphite crucible inside a high temperature furnace
for a temperature for about 600 to 650oc until the aluminum is melted. The reinforcing
materials such as titanium and boron carbide are mixed and are preheated at a
temperature of 450oc in a pre-heater furnace for 15 to 20 min. then the aluminum is
lifted off from the furnace and placed in the stir-casting furnace and the pre heated
reinforce materials are then mixed with the aluminum alloy where the temperature of
the furnace is maintained at a temperature of 760oc. the mechanical stirrer is inserted
into the crucible and the composition are stirred at a rpm of 400 for 10mins until the
materials are mixed the molten aluminum is poured in the die. The same process is
repeated with the composition of tungsten carbide and chromium.
Figure 1 stir casting furnace
4. HEAT TREATMENT’S
The heat treatments are done in a material to increase its grain structure and to make
the machinability of the material easy, the heat treatment also increases the
mechanical properties of the material, there are many types of heat treatment process
they are,
Annealing
Normalizing
Quenching
Case hardening.
MATERIALS Density
g/cm3
Tensile
strength MPa
Hardness
(rock well)
Melting point oc
Al 6061 2.70 125 30-33 580
Titanium 4.56 250 34 1668
Tungsten carbide 15.6 344 60 2830
Boron carbide 2.52 569 30 2763
Chromium 7.19 103 68 1857
Sivakumar.M, Vignesh.M, Sridhar.R, Sri Hari.K, RamaSubramanian.R
http://www.iaeme.com/IJMET/index.asp 236 [email protected]
Here we have done two heat treatment process of the above mentioned processes,
we have choose the process of annealing and quenching and the tensile test specimens
of the hybrid composites and pure aluminum are heat treated by the above two
mentioned process.
4.1. ANNEALING
Annealing is heat treatment process in which the material is heated form 2100 to 450
0c
for a duration of 0.5 to 2 hours and the material is cooled down in the furnace at a
temperature of 200c for 3 hours. This process increases the grain structure and
machinability of the material.
4.2. QUENCHING
Quenching is the process of heating the material up to the critical temperature of
about 6000c for about 3 hours and rapidly cooling it down to the temperature using the
water or oil bath or by using the vacuum. This process increases the grain structure
hardened the material and improve the machinability of the material.
5. TESTINGS DONE
There are several tests taken to determine the mechanical properties of the hybrid
composites. The test taken are the
Tensile test
Hardness(Rockwell)
Charpy test(impact test)
X-ray diffraction
Scanning electron microscopy.
5.1. Tensile test
The tensile test is done on the pure al 6061 and the other two hybrid composite with
three different specimens. The test specimens were heat treated before testing to
determine the heat treatment effect on the mechanical properties of the composite
materials. There are about three specimens taken from each composition. The
specimens were heat treated with different treatment methods such as “annealing” and
“quenching”. The specimens were tested with the universal testing machine, to
determine the point of break, elongation etc.,
Figure 2 tensile test specimen
Heat treatment effect on mechanical properties and SEM analysis of
Al6061/Wc/B4C/Ti/Cr metal matrix composites
http://www.iaeme.com/IJMET/index.asp 237 [email protected]
5.2. Impact test (CHARPY METHOD)
The impact test is taken the charpy test method as per the ASTM dimensions. The test
is taken for all the composition. The impact test results are compared between the
pure al 6061 and the hybrid composites.
Figure 3 impact test specimen
5.3. Hardness test (ROCKWELL HARDNESS)
Hardness test are taken for the samples of all compositions and these hardness are
compared with the hardness of the al6061. Here the hardness test is taken form the
“Rockwell hardness” methods.
Figure 4 The specimen for the hardness test
5.4. XRD ANALYSIS
The X-ray diffraction is a technique that is used to identify the materials composition
and the materials crystal structure and crystallography. Here in the X-ray diffraction
method a beam of X-ray is made to fall into the materials and this X-ray penetrates
the material and the report form a series of graphs with different profiles these profiles
shows a series of peaks, these peaks indicates the crystallite size and the lateral strain
on the material.
5.5. SEM ANALYSIS
The scanning electron microscopy is a method that is used to view the microstructure
of the material. In this method a strong beam of electron is projected into the material
and this electron beam is used examine the materials inner microstructure. The result
of the beam is viewed in the computer and the microstructure of the material is
identified.
6. RESULT DISCUSSIONS
6.1. IMAPCT TEST (CHARPY METHOD)
Impact test is done on the impact testing machine with the charpy method according
to the ASTM dimensions and standard’s. The specimen is placed in the charpy test
Sivakumar.M, Vignesh.M, Sridhar.R, Sri Hari.K, RamaSubramanian.R
http://www.iaeme.com/IJMET/index.asp 238 [email protected]
machine and the pendulum is fixed in the stand. The pendulum is released and they
are made to strike the specimen. The energy absorbed be the material during its
breakage is noted in the pointer and the calculation is done. The results obtained by
the charpy test is calculated and they are displayed in the table.
Table 3 Impact test results
The graph for the impact strength and toughness of the samples are graphed
below.
Figure 5 toughness in bar chart
6.2. HARDNESS (ROCKWELL HARDNESS)
The hardness of the material is calculated by the results obtained by the hardness scale
of the machine. The specimen is placed in the vice and the tester is made to touch the
surface of the material. This will show the hardness of the material in the scale
attached to the machine. The process is done for three trails and the average value of
the material is calculated and the calculated value is tabulated and the graph is drawn.
Table 3 hardness values
S.NO Composition Observed values,
HRB Average, HRB
1 Pure Al6061 30 31 30 31
2 Al6061+Ti+B4C 85 86 80 84
3 Al6061+Wc+Cr 78 75 80 78
S.NO Samples Toughness (MPa)
1 S1 29
2 S2 38
3 S3 37
Heat treatment effect on mechanical properties and SEM analysis of
Al6061/Wc/B4C/Ti/Cr metal matrix composites
http://www.iaeme.com/IJMET/index.asp 239 [email protected]
Figure 6 hardness in bar chart
6.3. TENSILE TEST
The tensile test of the materials are tested using the universal testing machine with a
capacity of 10 KN the materials are placed in the jaws of the machine are a load is
applied this load makes an elongation in the material this elongation of the material is
noted and the yield strength and the point of breaking are noted. This process is done
for the material of both composition and as well as for the pure Al6061 .The material
that heat treated are also tested. The result of the materials tensile load and elongation
and their point of breaking are calculated and a graph is drawn the results are
displayed in the table and the graph is showed that has the load applied in the
materials during the test.
The table shows the tensile strength of the three composition and their yield stress
at normal temperature.
Table 5 tensile strength at normal temperature
S.NO Composition Yield stress
N/mm2
Tensile strength
N/mm2
1 Al6061 120.124 133.073
2 Al6061+Ti+B4C 89.161 112.386
3 Al6061+Wc+Cr 114.222 142.885
The table below shows the tensile strength of the material after heat treated
(annealed specimen).
Table.6. tensile strength of the annealed specimens
S.NO Composition Yield stress
N/mm2
Tensile strength
N/mm2
1 Al6061 83.575 104.529
2 Al6061+Ti+B4C 102.54 131.162
3 Al6061+Wc+Cr 70.63 88.693
The table below shows the tensile strength of the materials and their yield stress
after heat treated (quenched).
Sivakumar.M, Vignesh.M, Sridhar.R, Sri Hari.K, RamaSubramanian.R
http://www.iaeme.com/IJMET/index.asp 240 [email protected]
Table 7 tensile strength of quenched specimens
S.NO Composition Yield stress
N/mm2
Tensile
strength N/mm2
1 Al6061 83.46 119.476
2 Al6061+Ti+B4C 76.076 95.839
3 Al6061+Wc+Cr 71.23 124.660
The graphs have been shown below comparing the tensile strength of the
materials.
Figure 7 tensile strength at normal temprature bar chart
Figure 8 tensile strength of annealed specimens bar chart
Figure 9 tensile strength of quenched specimens bar chart
Heat treatment effect on mechanical properties and SEM analysis of
Al6061/Wc/B4C/Ti/Cr metal matrix composites
http://www.iaeme.com/IJMET/index.asp 241 [email protected]
XRD ANLYSIS
The XRD analysis for the specimens are done in the x ray diffraction machine by
passing through a beam of xray in to the specimen and by identifying the amount of
the diffraction light emmited the graphs are drawn with the peaks in them this shows
the crystallite size and the lattice strain of the structure, the crystallite size and the
lattice strain of the specimens are calculated by the scherrer equation shown below, DP = 0.94 λ /β0.5cosθ
The lattice strain of the specimens are graphed by the values that we obtain from
the peaks of the xrd analysis
Figure 10 XRD peak graph of specimen 2
Figure 11 lattice strain chart
SEMB ANALYSIS
The SEM analysis results shows the crystal bonding between the base material and
the reinforcemnts shown in the SEM images, the SEM images of these specimens are
shown below,
Figure 12 SEM analysis of sample 1
Figure 13 SEM analysis of sample 2
Sivakumar.M, Vignesh.M, Sridhar.R, Sri Hari.K, RamaSubramanian.R
http://www.iaeme.com/IJMET/index.asp 242 [email protected]
Figure 14 SEM analysis of sample3
7. CONCLUSION
The significant conclusion of the studies are followed below,
1. The hybrid composite with the composition of al6061+Ti+B4C and al6061+Wc+Cr
are prepared by the stir casting process.
2. The mechanical properties of the cast composite materials are tested.
3. As far as we studied the heat treatment process have changed the physical and the
chemical properties of the materials.
4. The tensile strength values of the heat treated specimen varies as the heat treatment
process alters the grain structure of the material.
5. The lattice strain of the material is identified using the XRD testing and this shows
the sample 2 have the least strain and have the highest of hardness values.
6. The SEM analysis shows the boinding of the reinforcement materials with that of the
base material. And by this analysis we can be sure that the bonding between the
materials are very good in this method than the other methods.
REFERENCE
[1] Martin, J. Rodriguez, J. Llorca, “Temperature effects on the wear behavior of
particulate reinforced Al-based composites”, Wear, pp. 225–229 (1999).
[2] Szu Ying Yu, Hitoshi Ishii, Keiichiro Tohgo, Young Tae Cho, Dongfeng Diao,
“Temperature dependence of sliding wear behavior in SiC whisker or SiC
particulate reinforced 6061 aluminum alloy composite”, Wear 21: 21-28 (1997).
[3] M.K. Surappa, P. K. Rohatgi, Preparation and properties of cast aluminum-
ceramic particle composites, Journal of materials science, 16(1981), p 983-993.
[4] J.W. Kaczmar, K .Pietrzak, W. Wlosinski, The production and application of
metal matrix composite materials, Journal of material processing technology,
106(2000), p 106:58-67
[5] M.K. Surappa, P. K. Rohatgi, Preparation and properties of cast aluminum-
ceramic particle composites, Journal of materials science, 16(1981), p 983-993.
[6] Everett R.K and Arsenault R.J. “Metal Matrix Composites: Mechanisms and
Properties”, 1991 (Academic Press, San Diego). [2].
[7] Kocjak M.J., Kahtri S.C., Allison J.E and Jones J.W., “Fundamentals of Metal
Matrix Composites” (Ed S.Suresh, A.Mortensen and A.Needleman, 1993
(Butterworth- Heinemann, Boston
[8] K.Rajkumar (2013) “Mechanical and Machining Characteristics of AL/B4C
Metal Matrix Composites” National conference on Emerging trends in
mechanical engineering.
[9] T.S.Mahesh babu and N.Muthu Krishnan (2012) “Machinability behavior of PCD
1600 grade inserts on turning AL/SiC/B4C hybrid metal matrix composites”
International journal of Engineering Research and Applications.
Heat treatment effect on mechanical properties and SEM analysis of
Al6061/Wc/B4C/Ti/Cr metal matrix composites
http://www.iaeme.com/IJMET/index.asp 243 [email protected]
[10] Vibu Nanthan and Vidhusan “Machinability studies of turning
AL/SiC/B4Chybrid metal matrix composites using ANOVA analysis” ICTMME
july 15-16 2012
[11] The aluminum automotive manual Version 2002 © European Aluminum
Association.
[12] K.R. Padmavathi and Dr.R. Ramakrishnan, Aluminium Metal Matrix Composite
with Dual Reinforcement. International Journal of Mechanical Engineering and
Technology, 5(5), 2014, pp. 151–156.
[13] V.Suresh , Dr. R.Sivasubramanian , R.Maguteeswaran Study and Investigation of
Analysis of Metal Matrix Composite. International Journal of Mechanical
Engineering and Technology, 3(2), 2012, pp. 171–188
[14] Mechnanical and Physical Properties of Engineering Alumina Creamics, Vit
Tiedotteita- Meddelanden-Research Notes