THE EFFECT of INTERLAYERS on Dlsslmllar FRICTION WELD PROPERTIES
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THE EFFECT OF INTERLAYERS ON DlSSlMlLAR FRICTION WELD PROPERTIES Cuauhtemoc Maldonado-Zepeda A thesis subrnitted in conformity with the requirements for the degree of Doctor in Applied Science Graduate Department of Metallurgy & Materials Science University of Toronto O Copyright by Cuauhtemoc Maldonado-Zepeda (2001) National Library Bibliothèque nationale 1*1 of Canada du Canada Acquisitions and Acquisitions et Bibliographic Services services bibliographiques 395 Wellington Street 395. rue Wellington Ottawa ON K1A ON4 Ottawa ON KIA ON4 Canada Canada Your nk, Votm réldrmce Our bire None référence The author has granted a non- L'auteur a accordé une Licence non exclusive licence allowing the exclusive permettant à la National Libraqr of Canada to Bibliothèque nationale du Canada de reproduce, loan, distriiute or sell reproduire, prêter, distribuer ou copies of this thesis in microform, vendre des copies de cette thèse sous paper or electronic formats. la forme de microfiche/film, de reproduction sur papier ou sur format électronique. The author retains ownership of the L'auteur conserve la propriété du copyright in this thesis. Neither the droit d'auteur qui protège cette thèse. thesis nor substantial extracts f?om it Ni la thèse ni des extraits substantiels may be printed or otheTWise de celle-ci ne doivent être imprimés reproduced without the author's ou autrement reproduits sans son permission. autorisation. THE EFFECT OF INTERLAYERS ON DlSSlMlLAR FRICTION WELD PROPERTIES Doctor in Applied Science (2001) Cuauhtemoc Maldonado-Zepeda Graduate Department of Metallurgy & Materials Science University of Toronto ABSTUACT The influence of silver interlayers on the metallurgical and mechanical properties of dissimilar aluminium alloy/stainless steel friction welds are investigated. An elastic contact model is proposed that explains the conditions at and close to the contact surface, which produce A1D3 particle fracture in dissimilar MMCIAlSl 304 stainless steel friction welds. lntermixed (IM) and particle dispersed (PD) regions are forrned in Ag-containing dissimilar friction welds. These regions forrn very early in the joining operation and both contain AgdI. Therefsre, an interlayer (Ag) introduced with the specific aim of preventing Fe,AI, compound formation in MMCIAISI 304 stainless steel friction welds promotes the formation of anofher intermetallic phase at the bondline. Since IM and PD regions are progressively removed as the friction welding operation proceeds thinner interrnetallic layers are pmduced when long friction welding times are applied. ii This type of behavior is quite different from that observed in silver-free dissimilar MMWAISI 304 stainless steel welds. Nanoparticles of silver are formed in dissimilar MMC/Ag/AISI 304 stainless steel welds produced using low friction pressures. Nanoparticle formation in dissimilar friction welds has never been previously observed or investigated. The introduction of silver interlayers decreases heat generation during welding, produces narrower softened zone regions and improved notch tensile strength properties. Ali research to-date has assurned per se that joint mechanical properties wholly depend on the mechanical properties and width of the intemetallic layer fomed at the dissirnilar joint interface. However, it is shown in this thesis that the mechanical properties of MMC/AISI 304 stainless steel joints are determined by the combined effects of interrnetallic formation at the bondline and softened zone formation in MMC base maten'al immediately adjacent to the joint interface. A methodology for calculating the notch tensile strength properties of dissimilar friction welds is presented and is based on a combination of FEM with a ductile failure criterion. There is excellent correspondence behveen actual and calculated joint strength results. iii ACKNOWLEDGEMENTS Doy las gracias mas profundas por el invaluable apoyo recibido del pueblo de México a través dei Consejo Nacional de Ciencia y Tecnologia (CONACYT) y la Universidad Michoacana de San Nicolas de Hidalgo (UMSNH). ABSTRACT .................................................................................................................. II ACKNOWLEDGEMENTS ..................... .... ............................................................... IV TABLE OF CONTENTS .......................................................................................... v LIST OF TABLES ........................................................................................................ xi LIST OF FIGURES..................................................................................................... XII CHAPTER 1. THESIS PROPOSAL..................... ..... ................................................. 1 1. 1. INTRODUCTION.................................................................................................. 1 1.2. THE INTERLAYER APPROACH ......................................................................... 2 1.3. DETAILED THESIS OBJECTIVES..................................................................... 6 1.4. THE PROCEDURES ............................................................................................ 7 1.5. THESIS ORGANIZATION ................................................................................... 7 CHAPTER 2. THE FRICTION WELDING PROCESS .......................................... 9 2.1. INTRODUCTION................ .... ........................................................................ 9 2-1.1. lnertia friction welding .................................................................................. 1 O 2.1.2. Direct-drive fmion welding .......................................................................... 12 2.1 .2. i. Heating period ........................................................................................ 12 v 2.1 .2.2. Forging stage ......................................................................................... 16 2.1.2.3. Direct-drive friction welding parameten ............................~....................17 2.2. INTERMETALLIC COMPOUNDS IN DISSlMlLAR JOtNlNG ............................. 18 2.2.1 . Fe-AI intermetallic compounds ..................................................................... 18 2.2.2. Ni-AI intemetallic compounds ...................................................................... 20 2.2.3 .Ag-AI intermetallic compounds ................................................................... 21 2.2.5. Influence of composition on the intermetallic layer-...................................... 23 2.2.6. lntermetallic compounds and mechanical properties ................................... 25 2.3. FRICTION AND WEAR ...................................................................................... 27 2.3.7. SoR coatings and the coetficient of fn'cfion ................................................... 27 2.3.2. Wear and friction welding ............................................................................. 30 2.4. THERMAL ASPECTS OF FRICTION WELDING ............................................... 31 2.4.7. Calculafion of heat input in friction welding .................................................. 31 2.4.2. Temperature distribution during friction welding.................................... 33 2.5. WELDING METALLURGY OF ALUMINUM ALLOYS ........................................ 34 2.5.7. AI-Mg-Si Alloys ............................................................................................. 34 2.5.2 . Effect of the thermal welding cycle on dissolution and reprecipitation.......... 34 2.5.3. The softened zone ................................... ..,,.. ............................................... 36 2.6. MECHANICS OF SLlDlNG CONTACT .............................................................. 38 2.6.1. Line loading of a semi-infinite half-space ..................................................... 39 2.6.2. Torsional loading ............. .,. ......................................................................... 40 2.6.3. Normal pressure and torsional loading. ........................................................ 41 2.6.4. Contact of rigid-ideally-plastic materials .................... .. ............................. 44 2.6.4.1. Combined effect of shear and pressure on a plastic surface .................. 45 vi 2.6.4.2. The wave model ..................................................................................... 46 2.6.4.3. Wave removal model............................................................................. 48 CHAPTER 3. EXPERIMENTAL PROCEDURES ................... ..... ............................. 51 3.1. MATERIALS....................................................................................................... 51 3.2. FRICTION JOINING ........................................................................................... 54 3.3. METALLOGRAPHIC EXAMINATION ................................................................ 55 3.4. MECHANICAL TESTING ................................................................................... 58 CHAPTER 4 . INTERLAYERS AND PARTICLE FRACTURE IN DlSSlMlLAR FRICTION JOINTS ................... ................... ....................................................... 61 4.1. INTRODUCTION.......,....................................................................................... 61 4.2. RESULTS .......................... .... ..................................................................... 62 4.2.1. influence of friction