MICROSTRUCTURE AND MECHANICAL PROPERTIES IN FRICTION STIR WELDED TI-6AL-4V ALLOY

摘要

Ti and Ti alloys have high specific strengths and good erosion resistance, and thus have been widely used in the aerospace, chemical and nuclear industries. They are currently welded by a number of fusion welding processes, but some problems associated with fusion welding, such as formation of a brittle cast structure, large distortion and residual stress, still remain. Therefore, to avoid such problems, solid-state joining processes, such as friction stir welding (FSW), would be more suitable for joining Ti alloys. Some papers on FSW of Ti and Ti alloys have already shown some important knowledge on the microstructure and the properties in the welds, but effect of microstructure on mechanical properties of the weld has not been fully understood. The objective of the present study is to clarify relationship between microstructure and mechanical properties of friction stir welded Ti-6Al-4V alloy systematically.