Mechanical performance of heat treated Ti-6Al-4V Friction Stir Welds

Heat treatment processes for standard fusion welding techniques in titanium are well established, but the optimal heat treatment for Friction Stir Welded titanium has not been evaluated. In this study, 6 mm thickness titanium 6Al-4V butt welds were subjected to heat treatments ranging from 700 to 900 C. Results of the metallographic analysis for each heat treatment condition will be presented in addition to microhardness, tensile and fatigue properties. It was found that increased heat treatment temperatures lead to lower hardness and tensile strengths, higher elongation to failure and improved high cycle fatigue performance. Furthermore, fracture toughness and crack growth tests were performed for welds subjected to a standard post-weld stress relief. The fracture toughness was lower than the parent material, but crack growth rates in the weld were similar to that of the base metal.