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GEN-43.5 Characterization of Friction Stir Weld of Al6061/Al2O3p Metal Matrix Composites

Thursday, June 7, 2012: 3:25 PM
Sorrell 1 (Hilton Chicago/Indian Lakes Resort)
Dr. Jong-Ning Aoh , National Chung Cheng University, Minhsiung, Chiayi, Taiwan
Chih-Wei Huang , National Chung Cheng University, Minhsiung, Chiayi, Taiwan
Chun-Chieh Cheng , National Chung Cheng University, Minhsiung, Chiayi, Taiwan
Chin-Fa Huang , National Chung Cheng University, Minhsiung, Chiayi, Taiwan
Sy-Cherng Yang , Chung Shan Institute of Science and Technology, Lungtan, Taoyuan, Taiwan
Yue-Poe Huang , Chung Shan Institute of Science and Technology, Lungtan, Taoyuan, Taiwan

Particulate-reinforced metal matrix composite Al6061/Al2O3p is a light-weight high strength composite material. Friction stir welding is a potentially appropriate process for joining this composite which otherwise would be extremely difficult to be welded by arc welding process. We developed a FSW process by varying process parameters and tool design to butt weld Al6061alloy plate containing 10%, 15%, and 20% volume fraction of Al2O3 particles. Defect-free welds of elevated strength revealing onion rings and different flow patterns were obtained. A transverse section of the weld is shown in the figure. The hardness of the stir-zone is generally higher than that of the base metal. The hardness of the stir zone and the base metal after a PWHT was significantly improved. Tensile strength of the stir zone was maintained at the same level of the base metal. Higher volume friction of Al2O3 particle at 20% was not necessarily beneficial to the strength enhancement after FSW. Too high a welding speed decreased the hardness and volume of the stir zone. Investigation on tool dynamic load history during FSW revealed that tool load increased with increasing volume fraction of Al2O3 particles. An optimal process parameter combination also rendered an effective load reduction during FSW, as shown in figure, which not only allowed better material flow in the stir zone but also reduced tool wear. The tool wear increased with increasing rpm and decreasing welding speed. Optical micrographs revealed uniform particle distribution in the stir zone. Onion ring morphology was enhanced by the reinforced particles as shown in the figure. TEM on onion ring and on TMAZ revealed no adiabatic shear band formed at the stir zone/TMAZ boundary. Grain refinement and decrease in dislocation density were observed in the recrystallized stir zone.

Keywords:Friction stir welding, particulate-reinforced metal matrix composites, dynamic loading, microstructures, tool wear

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