Fatigue performance of Friction Stir Welded Ti–6Al–4V subjected to various post weld heat treatment temperatures

•Friction Stir Welding of Ti–6Al–4V butt joints.•Post weld heat treatment temperatures from 760 to 927°C.•High cycle fatigue testing.•Fatigue improved with heat treat temperature to within 20% of base metal. The purpose of this study was to evaluate a variety of post weld heat treatment temperatures on the fatigue performance of Friction Stir Welded Ti–6Al–4V joints in order to identify an optimal post weld heat treatment condition. Microstructure, microhardness and tensile properties were also evaluated for each heat treatment condition to provide additional insight into the fatigue results obtained. Four heat treatment temperatures were evaluated, 760, 816, 871 and 927°C. In general, it was found that that hardness and strength decreased with heat treatment temperature, but ductility and fatigue performance improved. It is recommended that a high heat treatment temperature be used on Ti FSW’s to obtain the best combination of strength, ductility and fatigue performance.