Fundamental Issues and Industrial Applications of Friction-Stir Welding
A wide range of the same and dissimilar metal and alloy systems were friction-stir welded in this investigation and their residual microstructures and hardness profiles examined and compared. The friction-stir weld (FSW) zone is characterized by dynamic recrystallization and in some cases, such as the FSW of silver to 2024 aluminum alloy, there is considerable grain growth of the silver. The FSW of age hardenable systems such as 6061 and 2024 aluminum alloys and a 6061Al + 20% Al10 J metal matrix composite, exhibit degradation of residual hardness (and strength) by as much as 45 percent from the base metal. However, in the welding of cast 11 00 aluminum alloy there was no loss in hardness while for the FSW of A339 aluminum alloy + 10% SiC the weld zone hardness actually increased noticeably from the base metal. For dissimilar systems involving an age-hardenable member or members the hardness reduction depended in part on the starting base metal hardness while in the case of pure metals or non-agehardenable alloys the lowest hardness was the limiting parameter. The FS\V of 606 1 AI/2024 AI, 2024 AI/Ag, 2024 AI/OI, 606 1AIIOI, and even aluminum alloy 606 1AI-20% AI10/ aluminum alloy A339- 10% SiC illustrates a wide range of industrial joining applications.