Project carried out at Indian Institute of Science, Bangalore

Project TeamAbhishek A.M. 1BY09ME004Harsha S 1BY09ME017N Sriram 1BY09ME031Supreeth Narasimhamurthy 1BY09ME050

Internal Guide External GuideDr. K.M. Sathish Kumar Dr. Satish V.KailasAssociate Professor, Mechanical Engineering Professor, Mechanical EngineeringBMS Institute of Technology Indian Institute of Science

Synthesis and Study of mechanical behaviour ofCopper-Ceramic composite using Nano-sized powders

INTRODUCTIONComposite materialsMaterials made from two or more constituent materials withsignificantly different physical or chemical properties, thatwhen combined, produce a material with characteristicsdifferent from the individual components. The individualcomponents remain separate and distinct within thefinished structure.

Metal-Matrix Composites (MMC)Metals and alloys are generally produced and shaped inbulk form but can also be intimately combined with anothermaterial that serves to improve their performance. Theresulting material is a Metal Matrix Composite

Why should we add ceramics to metals?• Additions to the metal confer high hardness and wear resistance.

• Hard carbide particles enhance the tool performance

• ceramic particle additions make it possible to increase the specific elastic modulus of metals and alloys.

• Alterations in physical properties such as their thermal conductivity or their coefficient of thermal expansion.

Literature Review

• K. Jia et al. (1998), investigated and compared the microstructure and mechanical properties of nanograin-sized WC-Co composites with those of conventional cermets .

• They discovered that the toughness decreases with increasing hardness in conventional composites, whereas the increase of hardness in nano-structured composites does not further reduce their bulk fracture toughness.

A. Miserez et al. in their study observed the effect of addition of ceramic to metal-matrix composites should not exceed 30% if the composite is intended for structural applications: otherwise its toughness and ductility generally become unacceptably low.

The researchers were able to experimentally prove this assumption by studying the mechanical behaviour of particle reinforced metals of varying ceramic content. This helped in deciding the optimum volume fraction of ceramic to be added in the composite.

• Sung-Tag Oh et al. in their research prepared powdered mixtures of Al2O3/Cu with a variation in particle size distribution and mixing homogeneity was obtained using different milling process and they achieved homogeneity of microstructure and high fracture strength.

• This study suggests that the particle size distribution and mixing homogeneity of powder mixture also must be considered for fabrication of Nano-composites with the desired microstructure and enhanced mechanical properties.

M. Sherif El-Eskandarany in his study employed high energy ball milling to fabricate the metal matrix composite (MMC) of Al reinforced with SiC particulate (SiC ) with distinct Nano crystalline characteristics.

Nano composites, aluminium reinforced with selected volume fractions, x (x=2, 5, 7, and 10) of particulate SiCwere fabricated by milling elemental powders of Al and SiC in a high-energy ball mill at room temperature.

This study suggests that mechanical alloying is an effective technique for the fabrication of nano-composites to get effective distribution of the reinforcement in the base metal and to get powders with nano-sized particles.

• Alexandrov et al. in their research used severe plastic deformation via high shear consolidation to consolidate nanometer-sized metallic powders and metal-ceramic nanocomposites at room temperature.

• Grain size was refined during the consolidation by the severe plastic torsional straining. The processed materials were very brittle, which was attributed partially to the oxidation of the initial nanometer sized powders.

Scope of Present WorkPRODUCTION OF POWDERSDetermination of the optimum parameters that is to be used for the synthesis of

Nano-sized powders.Production of Nano-sized powders of the copper-ceramic mixture using

mechanical alloying technique.Determination of the size of the particles in the powdered mixture using X-ray

diffraction technique.

CONSOLIDATION OF THE POWDERSFabrication of the dies and tools required for the compaction process.Consolidation of the powdered mixture by using high shear powder consolidation

technique.

HEAT TREATMENT AND TESTING OF THE COMPOSITESubjecting the green compact obtained to heat treatment for strengthening and

effective bonding.Preparation of the compact samples obtained for further testing.Mechanical testing and SEM imaging of the composite produced and comparison

with standard copper.

Present Work• In this project we select pure copper as the base metal

and a polymer derived ceramic (Cross-linked CERASET™ PDC) as the reinforcement. The amount of PDC to be added to the base metal is decided from the meticulous literature survey done earlier

Base Metal Pure Copper

Reinforcement Polymer Derived Ceramic- SiCN

Initial size of the Cu particles 44 microns

Compositions used 1. 8% vol SiCN in Cu

2. 20% vol SiCN in Cu

3. Pure Cu

Form of PDC Amorphous

PRODUCTION OF POWDERS

• For the production of powders, mechanical alloyingtechnique was used to mix the copper and ceramicpowders and reduce the size of the particles tonanoscale.

• First, the optimum parameters for the milling of thepowders were determined. The powders were milledin a planetary ball mill.

• After milling the size of the powders was determinedby X-ray diffraction process.

Ball Milling• The ball mill used in this experiment

was model PULVERISETT-7 from the classical line.

• The machine is suitable for the uniform and extremely fine attrition of very small samples of hard to soft grinding material, dry or in suspension, down to colloidal fineness for the mixing and perfect homogenizing of emulsions or pastes.

• The grinding sample is milled by high-energy impacts from grinding balls and friction between balls and the grinding bowl wall.

The pulverisette has twomilling stations on whichthe vials are loaded.

The vials are filled withcopper and ceramicpowders and stainlesssteel balls.

The ball to powder ratio isa very important parameterthat is to be controlled.

Total processing time 16 hrs (Milling time +

Idle time)

Total Milling time 8 hrs

Total Idle time 8 hrs

Time per cycle 30 min. (15 min. Milling

and 15 min. Idle)

No. of cycles 32

Milling speed 350 rpm

Type of milling Wet Ball Milling

Processing agent Toluene ( C7H8)

Ball to Powder Ratio 8:1

Weight of the balls per

vial

80 g

Weight of the powder

per vial

10 g

Material of the balls Stainless Steel

Material of the Vial Stainless Steel

PARAMETERS FOR BALL MILLING

X-Ray Diffraction

• After the milling process theresulting powders weresubjected to X-ray diffraction todetermine the size of theparticles and the homogeneityof the powdered mixture.

• The X-ray diffractometer usedfor this study is the PANalyticalX’Pert PRO.

Determination of Particle SizeThe x-ray diffractometer plots a graph of therelative intensity of x-rays vs the diffraction angle.From the graph obtained the size of the particlescan be calculated by using Scherrer’s equation,which is as followsD = (0.9*λ) / (β*cos(θ))Where,D- Particle size,λ - Wavelength of x-ray,β - Full Width at Half Maximum,2θ- Diffraction angle

Friction Stir Welder• The consolidation of powders is

done using a 5-axis friction stirwelder because it provides thenecessary axial and torsionalloads required for the high shearpowder consolidation process.

• BiSS friction stir welding testrigs feature high-stiffness;precision-aligned annular loadframe with 5 axis movementsand independently controlledservo-actuators using theadvanced features of the2370MS controller to providetranslation and deformationcontrol of each axis.

PARAMETERS FOR CONSOLIDATION OF POWDERS

Diameter of Die 1) 12 mm

2) 17 mm

Plunge Depth Depends on the die thickness, 6-7

mm less than the die thickness

Dwell time 1) 60 sec

2) 120 sec

3) 180 sec

4) 240 sec

5) 300 sec

Speed 1000 rpm

Rate 15 mm/min

Metallography• Belt Emery: Motor driven belt emery is used for fairly

coarse filing or machining or grinding with grit size of 80to obtain flat surface for polishing the specimen.

• Grinding: Hand grinding using Silicon Carbide abrasive(emery) papers was performed after belt grinding

• Polishing: Disc polishing machine was used for thispurpose. A fine powder of Silicon Carbide of 850 grit sizewas uniformly smeared on a clean billiard cloth, fixed tothe disk of the polishing machine.

• Etching: etching is done immersing the sample in theetchant, 50ml cold-saturated solution of sodium thiosulfatein distilled water with 1g of potassium metabisulphite for40-50sec with intermediate washing in running water.

SCANNING ELECTRON MICROSCOPY

• After polishing and etching,the microstructure of theconsolidated sample isobserved using the ScanningElectron Microscope(ESEMQUANTA 200 FEI)

• The surface of a specimen tobe examined is scanned withan electron beam, and thereflected beam of electrons iscollected, and then displayedat the same scanning rate ona cathode ray tube.

HEAT TREATMENT

• The consolidated green compact is subjected to heat treatment for strengthening and effective bonding.

• The electric furnace used for the heat treatment was manufactured by BAGSVIG

VICKER’S MICROHARDNESS TEST• The term microhardness test

usually refers to staticindentations made with loadsnot exceeding 1 kgf.

• The indenter is a Vickersdiamond pyramid

• The surface being testedgenerally requires ametallographic finish; thesmaller the load used, thehigher the surface finishrequired. Precision microscopesare used to measure theindentations

Results and ConclusionThe experiment was done using 3 samples• Pure copper• 8% volume of PDC copper composite • 20% volume of PDC copper composite

• The samples were consolidated using high shear pressure consolidation technique.

• The compacted samples were machined and subjected to further analysis

Analysis of pure copper (As received)• SEM image of As-received copper is shown below:

• The EDX spectrum of pure copper is shown

Analysis of Cross-linked PDC (As received)• SEM image of Cross-linked PDC is shown below

• EDX Spectrum of PDC

Milling of Copper with 8% vol PDC• Particle size was determined using XRD technique and

the XRD graph obtained is shown below:

Using Scherrer’s Equation, the size of the particles is obtained. The Scherrer equation is

d = (0.9*) / (*cos(θ))

Pos. [2θ.] FWHM Left [°2Th.] d-spacing [Å]

43.328440 0.356400 2.08659

50.406030 0.396000 1.80895

74.058330 0.633600 1.27910

• SEM image of nano-sized particles obtained

EDX spectrum of copper with 8 vol% PDC

Milling of Copper with 20% vol of PDC

• Particle size was determined using XRD technique and the XRD graph obtained is shown below:

Position [°2Theta] (Copper (Cu))

20 30 40 50 60 70 80 90 100

Counts

0

1000

2000

0.7

13

[°]

0.8

71

[°]

0.7

92

[°]

0.7

92

[°]

0.9

50

[°]

Cu 20% Vol PDC

Using Scherrer’s Equation, the size of the particles is obtained. The Scherrer equation is

d = (0.9*) / (*cos(θ))

Pos. [°2Th.] FWHM Left [°2Th.] d-spacing [Å]

43.720420 0.712800 2.06879

50.844790 0.871200 1.79436

74.355290 0.792000 1.27472

90.018350 0.792000 1.08919

95.472920 0.950400 1.04086

SEM image of nano-sized particles obtained

EDX spectrum of copper with 20% vol PDC

Consolidation of Pure Copper• The as-received copper powder was subjected to High

Shear Pressure Consolidation in the Friction Stir Welder (FSW). The parameters set were:

• Flat tool diameter- 16mm • Diameter of Die- 14mm• Dwell Time: 40sec• RPM-1000• Plunge Rate- 5mm/min

Fig 5.7: Pure copper consolidated sample

Cutting of the Die to remove the CompactDie after the consolidation of the compact

The final dimension of the compact obtained was:Diameter- 14.3mmThickness- 4.1mm

SEM image of compacted sample

Density measurement was done by using Archimedes principle

Wt in Air

(w1 gm)

Wt in Distilled Water

(w2 gm)

Density of Distilled Water(gm/cm3)

Final Density (gm/cm3)

3.8766 3.2671 0.996289 6.336692268

Compaction of Copper with 8% vol. PDC

• The 8 volume % PDC copper composite was then consolidated by a High Shear Pressure Consolidation technique in a Friction Stir Welding Machine. The powder was compacted by using the following parameters:

• Dwell Time: 40 sec• RPM-1000• Plunge Rate- 15mm/min• Diameter of die- 14mm• Flat tool Diameter- 16mm

Die after the consolidation of the compact

Consolidated Cu- 8volume % PDC composite sample

Microstructure of 8 volume% copper PDC composite

Density measurement was done by using Archimedes principle

Wt in Air

(w1 gm)

Wt in Distilled Water

(w2 gm)

Density of Distilled Water(gm/cm3)

Final Density (gm/cm3)

3.3216 2.7627 0.996289 5.921047669

AFTER HEAT TREATMENT

BEFORE HEAT TREATMENT

Wt in Air

(w1 gm)

Wt in Distilled Water

(w2 gm)

Density of Distilled Water(gm/cm3)

Final Density (gm/cm3)

5.6511 4.8413 0.996289 6.952492922

• Consolidation of this composition was done using the same parameters as before, but only the Dwell time was varied as follows

1. 60 sec2. 120 sec3. 180 sec4. 240 sec5. 300 sec

Consolidation of Copper with 20% vol. PDC

60 Sec

180 Sec

240 Sec120 Sec

4 Pass

300 Sec

Microstructure of 20 volume% copper PDC composite

EDX analysis of copper with 20 volume% PDC

keV0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00

CP

S[x

1.E

+3

]

0.0

0.2

0.4

0.6

0.8

1.0

001

CN

Cu

Cu

SiCu

Cu

Chemical formula mass% Atom% Sigma Net K ratio Line

C* 2.43 10.98 0.00 18658 0.0180770 K

N* 0.85 3.28 0.00 6129 0.0716463 K

Si 2.88 5.57 0.00 175236 0.3378983 K

Cu 93.84 80.17 0.00 827261 17.0628682 K

Total 100.00 100.00

• Density measurement was done by using Archimedes principle

Wt in Air

(w1 gm) Wt in Distilled Water

(w2 gm)

Density of Distilled Water(gm/cm3)

Final Density (gm/cm3)

2.7393 2.234 0.996289 5.401018123

ConclusionThe raw materials were characterised by using SEM and EDAX and the

properties were found to be desirable.Milling of the powders with varying compositions of PDC was carried out

by using a planetary ball mill and the size of the particles weredetermined by using X-ray Diffractometer. The particle size was found outto be 17 nm.

Consolidation of the milled powders was successfully carried out byHSPC technique in a Friction Stir Welding machine.

Density measurement of the compacted samples was carried out byusing Archimedes’ principle.

The consolidation parameters were varied in an attempt to improve theproperties of the composite.

The SEM images of the samples showed that a good homogeneity ofcopper and PDC was obtained.

•

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