Studies on processing of metal matrix composites.

STUDIES ON

PROCESSING OF METAL MATRIX COMPOSITES

PAWAN KUMAR MADAN

Thesis submitted

in fulfilment of the requirements for the Degree of

DOCTOR OF PHILOSOPHY

Department of Mechanical Engineering INDIAN INSTITUTE OF TECHNOLOGY, DELHI

NEW DELHI-11 001 6 IN D tA

JUNE, 1995

Dedicated fuimb%

in the fetus feet of

SUPREME FADIER

who mega& makes everything so possible

for me

....Truth which we all so much Cove, can never be comprehended with the physical instruments of science, nor can Ultimate Reality we so much adore be realized with the mental effort of philosophy.

Providence has located within the human body a special spiritual faculty, and it is the excfusivefunction of religion to teach man ad about that faculty.

When that faculty is devethped in us like the p [tyska( and mental-faculties, we shaft be ab k to perceive Truth and realize Ultimate Reality in the same manner as we now perceive and realize the sun with our physical. eyes.

And when this takes place, you will both be astonished and amused to find that Truth - thegoar of Science, Ultimate Reality- thegoal of Philosophy, and God- the goat- of ReiWon, are but three names of the Supreme Essence.

CERTIFICATE

This is to certify that the thesis entitled "Studies on Processing of Metal Matrix composites" by Pawan Kumar Madan submitted to the Indian Institute of Technology, Delhi, India, for the award of the degree of Doctor of Philosophy in Mechanical Engineering Department is a record of bonafide research work carried out by him under my supervision and guidance. The thesis work, in my opinion, has reached the standard fulfill ing the requirements for the Doctor of Philosophy Degree.

The research report and results presented in this thesis have not been submitted in part or in full to any other University or Institute for the award of any degree or diploma.

Dated : 26th July, 1995. (Dr. R. Sagar) Assistant Professor

Department of Mechanical Engineering Indian Institute of Technology

New Delhi - 110016 (India)

ACKNOWLEDGEMENTS

Exposure to the overwhelming freedom of independent research and the subsequent requirement to demonstrate ones ability to make an original contribution to human knowledge is perhaps the greatest academic challenge one faces during the course of doctoral research work. Although virtually no one meets this challenge without sacrificing a great deal of time, leisure and immediate reward, there would be few who would not find the achievement well worth the sacrifice in terms of sheer intellectual satisfaction.

It is a great pleasure to express my sincere gratitudes to Dr. R. Sagar, Assistant Professor of Mechanical Engineering, for his invaluable guidance and help throughout the investigation.

I am specially indebted to Prof. B. L. Juneja, Prof. R. N. Mittel, Prof. U. R. K. Rao, Prof. R. K. Pandey and Prof. S. T. Jilani for their continual encouragement, many valuable discussions, criticism throughout this work and sincere help to bring out the thesis in the present form.

I also express my deepest sense of gratitude to Prof. A. D. Damodaran, Director, Dr. B. C Pai, Dr. R. M. Pillai, Dr. K. G. Satyanarayana, Dr. U. T. S. Pillai, Mrs. Geetha Ramani and Mr. Ravi Kumar, Regional Research laboratory, Trivandrum for introducing me to the field of composites and their invaluable help and suggestions.

I extend my sincere thanks to Dr. A. K. Gupta, Head, Mechanical Processing Activity, National Physical Loboratory, New Delhi, for his kind help and cooperation.

I wish to accord my heart-felt thanks to Mr. P. K. Ratnaparkhi, Director, Mr. M. P. Kawthekar, Manager R & D, Electronica Machine Tools, Pune, for their cooperation.

On a more personal note, I would like to thank Dr. S. S. A. Ravi, Dr. A. V. S. R. K.

Prasad, Dr. Sukhdev Roy, Mr. C. M. Markan, Mr. G. Manidhar, Mr. T. Prasad, Mr Deepak Dogra, Mr. M. M. Verma, Mr. Ramesh.C, Mr. Mahesh. K, Mr. Suresh.T and Mr. U. K. Bishnoi for their valuable assistance throughout the course of this research work.

I also thank the staff of Machine Tool, Production Engineering, Metrology, Welding, Foundary, Forging, Numerical Control, Cybernatics, Strength of Matrial, Friction & Wear and I.D.D.C, laboratories for their cooperation and active help.

I owe special thanks to Dr. K. Kumar, Director, Engineering Department, Maruti Udyog Ltd., Gurgaon and Mr. G. Subrahmanya, Asst. General Manager, Engineering Department, Mr. G. Sambiah, General Manager, Quality control, Mr. S. B. Gupta, Deputy General Manager, R & D and Mr. Ramesh. V., Manager, R & D, Hero Honda Motors Ltd. Dharuhera, Mr. Kuldeep Dhingra, Manager, Sunbeam Castings, Gurgaon for providing me with the instrumentation and other facilities under their charge.

I take this opportunity to express deep sense of gratitude to my parents, who gave me everything they could, to make me what I am today. I also have the affection of my sister and best wishes of my brother-in-law all along. Their touching care and love provided me the necessary strength to withstand the pressures of my research program. Their contributions to this work, though invisible, are invaluable to me.

Thanks are also due to Mrs. & Mr. Dinesh Rajput for typing the manuscript and Mr. Manoj Bhardwaj for drafting the drawings.

Last but not the least, I would like to thank all my satsangi brothers and sisters who helped me in one way or other.

New Delhi

26th July, 1995. Pawan Kumar Madan

iii

ABSTRACT

In the present research work efforts have been made in the following directions :

1. Preparation and properties of Al-SiCp, 6061AI-SiCp, 6061A1-10vol% A1203 and 2014A1- 20vol% A1203 composites.

2. Turning of 6061 Al -SiCp, 6061 Al-10 vol% A1203 and 2014 AI-20 vol% A1203 composites.

3. Electrical Discharge Machining (EDM) of 6061AI -SiCp, 6061A1-10 vol% A1203 and 2014A1-20 vol% A1203 composites.

4. Industrial applications of 6061A1-SiCp, 6061AI-10 vol% A1203 and 2014A1-20 vol% A1203 composites.

1. Preparation and properties of Al-SiCp, 6061A1-SiCp, 6061A1-10vol% A1203 and 2014A1- 20vol% A1203 composites : Al - SiCp compacts were synthesized by powder metallurgy technique. Commercial grade aluminium powder and SiC particles were sieved separately to obtain a grain size of 75-150 j.tm respectively. Blends of four different compositions were prepared i.e 10, 20, 30 and 40 wt % Si Cp. These blends were cold isostatically compacted using compound cylinder and plunger at a pressure of 625 MPa and sintered.

6061 Al-SiCp composites were synthesized through liquid metallurgy route. About 3wt% magnesium was added to the melt to improve wettability between ceramic particles and aluminium alloy. Pretreated SiCp (23prn)were introduced into the molten alloy while the melt was stirred using an impeller. Four ingots of 6061 Al alloy and 6061 Al alloy reinforced with 5,10 and 15wt % SiCp were cast. These ingots were homogenised at 480°C for 96 hours and hot extruded. The extrusion ratios obtained were 16:1 and 36:1. The 6061AI alloy and 6061A1 alloy reinforced with 5, 10 and 15 wt % SiCp specimens cut from the respective extruded rods were later solutionized and aged to T6 conditions. The extruded rods of (4)50mm x 600mm) 6061A1-10vol% A1203 and 2014A1-20vol% A1203 were supplied by DURALCAN USA.

Mechanical properties like density, micro-macro hardness, elastic modulus, compressive, tensile and impact strengths were measured. The coefficient of thermal expansion, thermal and electrical conductivities of 6061 Al-SiCp, 6061AI-10 vol% A1203 and 2014A1-

20 vol% A1203 composites were also measured. Scanning electron microscope was used to visualise the distribution of SiCp in the as cast, extruded and aged conditions. Tensile fractured surfaces were also analysed. Base material compostion was found out using spectrometer. Flow of particles during extrusion was also studied.

Turning of 6061 Al -SiCp, 6061 A1-10 vol% A1203 and 2014 A1-20 vol% A1203 composites : 6061 Al alloy reinforced with 5, 10 and 15 wt% SiCp, 6061 A1-10 vol% A1203 and 2014 A1-20 vol%A1203 extruded rodswere turned on NH22 HMT Centre lathe. Machinability was assessed using cemented carbide inserts SNMG 120408 E of THM grade (ISO K10 - K20) clamped in MSBNR 2525 M12 tool holder. A first order three variable empirical equation to study the effect of depth of cut, feed and cutting speed on cutting force was developed. A 23 factorial design was used for above analysis. The cutting force values obtained both by theory and experiment were compared.

The effect of cutting speed, depth of cut and feed on cutting force, surface roughness, tool wear and tool life was investigated. Flank wear criterion of VB = 0.3 mm was taken for calculating the Taylor's exponent. An assessment of the quality of the workpiece and tool surfaces were made using a scanning electron microscope. The built-up edge formation was also investigated.

3. Electrical Discharge Machining (EDM) of 6061A1 -SiCp, 6061A1-10 vol% A1203 and 2014A1.20 vol% A1203 composites : An investigation has been made into the feasibility of using EDM as a means of machining metal matrix composites (6061 Al-SiCp, 6061 A1-10 vol % A1203 and 2014 AI-20 vol % A1203 ). Machining was performed at various currents, pulse durations, gap voltages, duty factors and at different polarities using copper and graphite tools. Technology charts were prepared in terms of material removal rate, wear ratio, surface roughness and overcut against the machining parameters. As far as possible, standard test conditions laid down by C.1.R. P. (STC 'E' group) were followed [2681

Several mathematical models, based on the thermal phenomena associated with the process of metal removal by EDM were studied for qualitative description of the EDM

process. A uni-dimensional and two dimensional heat transfer models considering the plasma channel to be plane heat and disc heat source respectively have been employed to study the effects of EDM input parameters such as, pulse duration, pulse energy and material properties on important process parameters such as, the maximum temperature attained at the surface, heating rate on the surface, the temperature gradient, the critical powerdensity and the pulse duration required for metal melting. Two dimensional model has been refined to incorporate the effects of metal evaporation and plasma channel expansion during the discharge. Plasma channel growth was computed for different tool materials.

Scanning electron microscopic examination highlighted the important features of electrical discharge machined surfaces. Micro-hardness measurements were also performed on the as machined composites.

4. Industrial applications of 6061A1-SiCp, 6061A1-10 vol% A1203 and 2014AI- 20vol%A1203 composites : Few pistons and liners were cast and machined from 6061A1- 1 Owt% SiCp and 6061A1-15wt% SiCp composite materials respectively. A4)150 mm, 25 mm thick and 3.175 mm module gear was cast and machined from 2014 A1-20 vol% A1203 composite. Precision gears and intricate shapes made from 6061 Al-Si C composites were machined by wire EDM. Clamping pads were fabricated from 2014AI-20 vol% A1203 and 6061AI-15 wt% SiCp composite materials. Half Nuts and threaded fasteners were also fabricated from 6061A1-SiCp composites.

CONTENTS

Page No.

CERTIFICATE

ACKNOWLEDGEMENTS ii

ABSTRACT iv

CONTENTS vii

LIST OF FIGURES xv

LIST OF TABLES xxxi

NOMENCLATURE xxxv

CHAPTER I INTRODUCTION

1.1 THESIS LAYOUT CHAPTER II LITERATURE SURVEY

1 3 6

2.1 INTRODUCTION 6

2.2 MATERIALS 7

2.2.1 Matrix Alloys 7

2.2.2 Reinforcements 7

2.2.2.1 Carbides 10

2.2.2.2 Nitrides 10

2.2.2.3 Oxides 10

2.3 FACTORS AFFECTING THE UNIFORM 10 DISTRIBUTION OF SECOND PHASE PARTICLES

2.3.1 Wetting of the Particles with the Matrix 10 2.3.2 Particle Size Distribution 12

2.3.3 Density Difference 13

2.3.4 Stirrer Geometry and Method of Stirring 14 vii

2.3.5 Casting Fluidity 14

2.3.6 Microstructure 15

2.4 FABRICATION OF METAL MATRIX PARTICULATE 17 COMPOSITES

2.4.1 Powder Metallurgy 17

2.4.2 Solidification Processing 20

2.4.2.1 Dispersion Processes 20

2.4.2.1.1 Stir Casting 21

2.4.2.1.2 Compocasting 21

2.4.2.1.3 Multi Random Rotation 22

2.4.2.2 Pressure Impregnation 22

2.4.2.2.1 Squeeze Casting 23

2.4.2.2.2 Pressure Infiltration 25

2.4.2.2.3 Lanxide Process 25

2.4.2.3 Spray Deposition 25

2.4.2.3.1 Osprey Process 26

2.5 STRUCTURAL DEFECTS IN CAST METAL MATRIX 29 PARTICULATE COMPOSITES

2.5.1 Porosity 29

2.5.2 Particle Segregation 31 2.5.3 Interfacial Reactions 32

2.6 SECONDARY PROCESSES 32

2.7 MECHANICAL PROPERTIES OF AI-SIC 36 COMPOSITES

2.7.1 Tensile Properties 37 2.7.2 Compressive Properties 41

2.8 TURNING OF METAL MATRIX COMPOSITES 42

2.8.1 Cutting Forces 43

2.8.2 Tool Wear and Tool Life 43

2.8.3 Surface Finish 46

2.8.4 Microstructure of Machined Surface 48 2.9 ELECTRICAL DISCHARGE MACHINING OF METAL 50

MATRIX COMPOSITES

2.9.1 Historical Developments of EDM Process 52 2.9.2 Factors Affecting Machining Rate 52 2.9.3 Factors Affecting Tool Wear 53 2.9.4 Factors Affecting Reproduction Accuracy 54

2.9.5 Thermal Modelling 57

2.9.5.1 Plane Heat Source 58

2.9.5.2 Point Heat Source 58

2.9.5.3 Circular Heat Source 60

2.9.6 Surface Integrity in ED Machined Specimens 61 2.9.7 Electrical Discharge Machining of Carbides 62

and Metal Matrix Composites

2.10 APPLICATIONS 66

2.11 SUMMARY 73

CHAPTER III PREPARATION AND PROPERTIES OF Al-SiC , 6061AI- 75 SiC 6061A1-10vol% AI203 AND 2014A1-20vol% A1203

COMPOSITES

3.1 INTRODUCTION 75

12 EXPERIMENTAL' 75

3.2.1 Materials 75

ix

3.2.2 Preparation of Al-SiC Composites through 78 Powder Metallurgy Route

3.2.3 Preparation of 6061AI-SiCp Composites 79 through Liquid Metallurgy Route

3.2.4 Extrusion of 6061AI-SiCP Composites 86

3.2.5 Age Hardening 90

3.2.6 Microscopy 91

3.2.7 Mechanical Properties 91

3.2.7.1 Density 91

3.2.7.2 Hardness 91

3.2.7.3 Tensile Properties 92

3.2.7.4 Compression Properties 92

3.2.7.5 Impact Strength Properties 94

3.2.8 Thermal Properties 94

3.2.8.1 Coefficient of Thermal Expansion 94

3.2.8.2 Thermal Conductivity 94

3.2.9 Electrical Properties 96

3.2.9.1 Electrical Resistivity 96

3.3 RESULTS 97

3.3.1 Preparation of Composites 97 3.3.2 Extrusion of 6061AI-SiCP Composites 99

3.3.3 Age Hardening 102

3.3.4 Microstructure 104

3.3.5 Mechanical Properties 107

3.3.5.2 Hardness 117

3.3.5.3 Tensile Properties 117

3.3.5.4 Compressive Properties 136

3.3.5.5 Impact Strength Properties 136 3.3.6 Thermal Properties 143 3.3.6.1 Coefficient of Thermal Expansion 143

3.3.6.2 Thermal Conductivity 145

3.3.7 Electrical Properties 147 3.3.7.1 Electrical Resistivity 147 CHAPTER IV TURNING OF 6061A1-10vol% A1203, 2014A1-20vol% A1203 150

AND 6061AI-SiC COMPOSITES

4.1 INTRODUCTION 150

4.2 EXPERIMENTAL 150

4.2.1 Workpiece Material 150 4.2.2 Cutting Tool and Tool Holder 150

4.2.3 Turning Tests 150

4.2.4 Cutting Force Measurement 153 4.2.5 Tool Wear and Tool Life 155 4.2.6 Surface Roughness Measurement 155 4.2.7 Microstructure of Machined Surface and 155

Chip Collection

4.2.8 Design of Experiments 155

4.2.8.1 Postulation of Model 156

4.2.8.2 Analysis of Variance 158

4.2.8.3 Confidence Interval 158

xi

4.3 RESULTS 159 4.3.1 Cutting Force Analysis 159 4.3.1.1 Error Sum of Square Calculations 165 4.3.1.2 Analysis of Variance for Checking the 165

Adequacy of the Postulated Model

4.3.1.3 Confidence Interval 168

4.3.1.4 Confirmatory Tests 168

4.3.2 Tool Wear and Tool Life 173

4.3.3 Surface Roughness 188

4.3.4 Dimensional Accuracy 199 4.3.5 Microstructure of Machined Surface and 199

Chip Formation

CHAPTER V ELECTRIC DISCHARGE MACHINING OF 6061AI-SiC , 207 6061A1-10vol% A1203 AND 2014A1-20vo1% Al2d3

COMPOSITES

5.1 INTRODUCTION 207

5.2 EXPERIMENTAL 207

5.2.1 Workpiece Material 207

5.2.2 Tool Material 207

5.2.3 EDM Tests 208

5.3 THERMAL ANALYSIS OF EDM PROCESS • 221 5.3.1 Uni-dimensional Heat Source Model 223 5.3.2 Disc Heat Source Model 232

5.4 EXPERIMENTAL RESULTS 245

5.4.1 Material Removal Rate 247

5.4.2 Wear Ratio 263

5.4.3 Surface Roughness 276

5.4.4 Overcut 289

5.4.5 Taper 298

5.4.6 Surface Integrity of EDM'ed Surfaces 300 Chapter VI INDUSTRIAL APPLICATIONS OF 6061AI-SiC and 2014AI- 311

20vol% A1203 COMPOSITES

6.1 INTRODUCTION 311

6.2 FABRICATION 311

6.2.1 Piston 311

6.2.2 Cylinder Liner 313

6.2.3 Gear 314

6.2.4 Clamping Pads 319

6.2.5 Half Nuts 323

6.2.6 Threaded Fasteners 324

6.3 RESULTS 324

6.3.1 Piston and Cylinder Liner 324

6.3.2 Gear 329

6.3.3 Clamping Pads 331

6.3.4 Half Nuts 331

6.3.5 Threaded Fasteners 33

CHAPTER VII CONCLUSIONS AND SCOPE FOR FURTHER WORK 334

7.1 CONCLUSIONS 334

7.2 SCOPE FOR FURTHER WORK 339

REFERENCES 341

APPENDIX 1 359

APPENDIX II 361

APPENDIX III 373

APPENDIX IV

LIST OF PUBLICATIONS FROM THE PRESENT WORK 380

CURRICULUM VITAE 381