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Mechanical Testing and Evaluation of High-Speed and Low MECHANICAL TESTING AND EVALUATION OF HIGH-SPEED AND LOW- SPEED FRICTION STIR WELDS A Thesis by Nitin Banwasi Bachelor of Engineering, Bangalore University, Bangalore, India 2000 Submitted to the College of Engineering and the faculty of the Graduate School of Wichita State University in partial fulfillment of the requirements for the degree of Master of Science Fall 2005 EXPERIMENTAL TESTING AND EVALUATION OF HIGH-SPEED AND LOW- SPEED FRICTION STIR WELDS I have examined the final copy of this thesis for form and content and recommend that it be accepted in partial fulfillment of the requirements for the degree of Master of Science, with a major in Mechanical Engineering. George E. Talia, Committee Chair We have read this thesis and recommended its acceptance: Dr. Hamid M. Lankarani, Department Chair, Committee Member Dr. Krishna K. Krishnan, Committee Member ii DEDICATION To My Parents iii ACKNOWLEDGEMENTS I am grateful to all that are part of my efforts during my work both academically and personally. I am thankful to my committee chair, Dr.George E.Talia, for being not only supportive in my endeavors but also patient and informative. I appreciate the involvement of both Dr. Hamid M. Lankarani and Dr. Krishna K. Krishnan for their involvement in its fulfillment. I also want to remember fellow student’s help and suggestions in making it possible with gratitude. iv ABSTRACT The potential of the Friction Stir Welding (FSW) process is easily observed in the creation of defect free welds in almost all of the Aluminum alloys. The success and applicability of the process, however, will depend on the performance of the welds compared to other joining processes. Experimental testing and evaluation are necessary for the determination of the mechanical response of Friction Stir Welds and vital to the development and optimization of the FSW process. The goal of this experimental testing of Friction Stir Welds is to obtain the data necessary to begin understanding the effects of the FSW process. An attempt has been made to systematically examine the effects of FSW process parameters and alloy on the weld properties. An attempt has been made to evaluate and compare High Speed and Low Speed Friction Stir Welds. v TABLE OF CONTENTS 1. INTRODUCTION 1 1.1. Welding 3 1.2. The physical nature of joining 4 1.3. Welding, from a metallurgical point of view 4 1.4. A metallurgical classification of the welding processes 5 1.5. Types of welding 5 1.6. Solid state welding 7 1.7. Friction welding 7 1.8. Rotary friction welding 8 2. ALUMINUM WELDING 2.1. Introduction 9 2.2. Characteristics of Aluminum 10 2.3. Aluminum alloy designation – wrought alloys 11 2.4. Nonheat treatable Aluminum alloys 12 2.5. Heat treatable Aluminum alloys 12 2.6. Wrought Aluminum alloys 12 2.7. Welding Aluminum 14 3. FRICTION STIR WELDING 3.1. Introduction 17 3.2. Different parameters in FSW 18 3.3. Process advantages 20 3.4. Microstructure classification 22 vi 3.5. Joint geometries 24 3.6. Applications 25 4. MECHANICAL TESTING AND METALLOGRAPHY 4.1. Testing 28 4.2. Tensile Test 28 4.3. Tensile Specimens 29 4.4. Hardness Test 30 4.5. Types of hardness tests 31 4.6. Factors for selection of hardness testing methods 32 4.7. Rockwell hardness test 32 4.8. Metallographic specimen preparation basics 34 5. EXPERIMENTAL PROCEDURE 5.1. Tensile test 37 5.2. Hardness test 37 5.3. Metallographic analysis 38 6. RESULTS AND DISCUSSIONS 6.1. Effect of changing welding speed at constant weld pitch 40 6.2. Temper effects on required loads and weld energy 41 6.3. Alloy effects on specific weld energy 42 6.4. Low-speed friction stir weld 1 43 6.5. Low-speed friction stir weld 2 47 6.6. Low-speed friction stir weld 3 53 6.7. Low-speed friction stir weld 4 64 vii 6.8. Low-speed friction stir weld 5 69 6.9. Low-speed friction stir weld 6 73 6.10. Low-speed friction stir weld 7 77 6.11. Low-speed friction stir weld 8 81 6.12. Low-speed friction stir weld 9 88 6.13. Low-speed friction stir weld 10 92 6.14. Tool geometry effects 97 6.15. High-speed friction stir weld 11 100 6.16. High-speed friction stir weld 12 104 6.17. High-speed friction stir weld 13 107 6.18. High-speed friction stir weld 14 110 6.19. High-speed friction stir weld 15 116 6.20. High-speed friction stir weld 16 118 6.21. High-speed friction stir weld 16 119 7. CONCLUSIONS AND FUTURE SCOPE 121 8. REFERENCES 125 viii LIST OF FIGURES 1.1. Friction stir welding process 2 1.2. Master chart of welding and allied processes 6 1.3. Friction stir welding and processing technologies 8 3.1. Friction stir welding 18 3.2. Microstructure of a friction stir weld 20 4.1. Tensile test specimen 29 4.2. Rockwell principle 33 6.1. Required energy and specific weld energy at constant weld pitch 40 6.2. X-axis force for welds made at constant weld pitch 41 6.3. Specific weld energy as a function of welding speed 42 6.4(a). Hardness graph – across the weld 46 6.4(b). Microstructure of the weld 47 6.5(a). Hardness graph – across the weld @ 10”/min 52 6.5(b). Hardness graph – across the weld @ 15”/min 52 6.6(a). Hardness graph – across the weld @ 10”/min 58 6.6(b). Hardness graph – across the weld @ 15”/min 58 6.6(c). Peak/Yield stress of the weld – 10”/min @ 750, 760 & 600 rpm 59 6.6(d). Break stress of the weld – 10”/min @ 750, 760 & 600 rpm 60 6.6(e). Weld 2 – change in stress due to change in welding pitch 61 6.6(f). Weld 3 – change in stress due to change in welding pitch 62 6.6(g). Weld 2 & weld 3 – change in hardness due to change in welding pitch 63 6.7(a). Hardness graph – across the weld 67 ix 6.7(b). Microstructure of the weld nugget 68 6.8(a). Hardness graph – across the weld 72 6.8(b). Microstructure of the weld 73 6.9(a). Hardness graph – across the weld 76 6.10(a). Hardness graph – across the weld 80 6.11(a). Hardness graph – across the weld 84 6.11(b). Peak/yield stress variation 85 6.11(c). Break stress variation 85 6.11(d). Variation in hardness 86 6.12(a). Hardness graph – across the weld 91 6.12(b). Microstructure of the weld nugget 92 6.13(a). Hardness graph – across the weld 95 6.13(b). Microstructures of the weld 96 6.14(a). Specific weld energy as a function of welding speed and tool geometry 97 6.14(b). Required weld power as a function of tool geometry and welding speed 98 6.14(c). Transverse tensile strength of the welds as a function of tool geometry and welding speed 99 6.14(d). X axis force as a function of tool geometry and welding pitch 99 6.15(a). Hardness graph – across the weld 103 6.15(b). Microstructure of the weld 103 6.16(a). Microstructure of the weld nugget 106 6.17(a). Microstructure of the weld nugget 109 6.18(a). Hardness graph - across the weld 113 x 6.18(b). Microstructure of the weld 113 6.18(c). Variation in peak and yield stress 114 6.18(d). Variation in break stress 114 6.18(e). Variation in hardness 115 xi LIST OF TABLES 6.4(a). Tensile test data of parent 1 – Alclad 2024-T3 43 6.4(b). Tensile test data of parent 2 - Al 7075-T6 44 6.4(c). Tensile test data of the weld 44 6.4(d). Hardness test data – along the weld 45 6.4(e). Hardness test data – across the weld 46 6.5(a). Tensile test data of parent 1 – Alclad 2024-T3 48 6.5(b). Tensile test data of parent 2 – Al 7075-T6 48 6.5(c). Tensile test data of weld @ 10”/min 49 6.5(d). Tensile test data of the weld @ 15”/min 49 6.5(e). Hardness test data – along the weld 51 6.5(f). Hardness test data – across the weld 51 6.6(a). Tensile test data of parent1 – Alclad 2024-T3 54 6.6(b). Tensile test data of parent 2 - Al 7075-T6 54 6.6(c). Tensile test data of the weld @10"/min 55 6.6(d). Tensile test data of the weld @ 15"/min 55 6.6(e). Hardness test data - along the weld 57 6.6(f). Hardness test data - across the weld 57 6.7(a). Tensile test data of parent1 - Alclad 2024-T3 64 6.7(b). Tensile test data of parent 2 - Al 7075-T6 65 6.7(c). Tensile test data of the weld 65 6.7(d). Hardness test data- along the weld 66 6.7(e). Hardness test data - across the weld 67 xii 6.8(a). Tensile test data of parent1 – Alclad 2024-T3 69 6.8(b). Tensile test data of parent2 - Al 7075-T6 69 6.8(c). Tensile test data of the weld 70 6.8(d). Hardness test data – along the weld 71 6.8(e). Hardness test data – across the weld 71 6.9(b). Tensile test data of the parent – Al 6061-T6 74 6.9(b).
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