Effect of welding ways on microstructure and mechanical properties of 6082 aluminum alloy

Friction-stir welding (FSW) of 6082 aluminum alloy was welded by conventional FSW and bobbin-tool FSW.Microstructure and mechanical performance of the as-prepared joints samples were examined.Some inside-out onion rings can be observed in the cross section of bobbin-tool FSW joints samples in microstructure analysis.Microstructure of nugget and TMAZ are obviously different,which shows the evolution of the microstructure.The results indicate that the general mechanical properties of samples prepared by conventional FSW are better than that by bobbin-tool FSW.Sample prepared by bobbin-tool FSW has a finer average grain size than that by conventional FSW.The cavities in the fracture appearance of bobbin-tool FSW joint sample are shallower and there are some smooth platform which are similar to the quasi-cleavage crack near these cavities.While the deeper cavities can be observed in the fracture appearance of conventional FSW joint sample.The lowest hardness point of bobbin-tool AA 6082 FSW joint sample is located in the TMAZ,and hardness in the upper WNZ zone is the highest.