Study on Multi-Zone Mechanical Properties of Friction Stir Weld of 5083 Aluminum Alloy
Microstructure observation,tensile test,hardness test and fatigue test were carried out for different areas of the 12 mm thick 5083 aluminum alloy bobbin tool friction stir welding joint.The fracture of the specimens after fatigue test was observed by SEM.The results show that the grains in the weld nugget area are obviously refined,the grains in heat affected zone are coarsened,and the grains in heat-mechanical affected zone are severely deformed and have directionality.The overall hardness distribution of the joint is approximately asymmetric W-shaped.The hardness from the base metal to the weld nugget zone is first reduced and then increased.The hardness of the base metal is the highest,followed by the welding nugget zone.The fatigue life of the base metal,the weld nugget zone,and the heat affected zone are quite different.The fatigue performance of the base metal is the best,that of the weld nugget zone is the second,and that of the heat affected zone is the weakest.The source of fatigue cracks in each zone is generated on the surface of the fatigue specimen.Fatigue bands can be seen in the expansion zone,and the fracture mode of the instantaneous fracture zone is ductile fracture.
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