Microstructural evolution and mechanical properties of a linear friction welded two-phase Ti-6.5Al-3.5Mo-1.5Zr-0.3Si titanium alloy joint

The microstructure, microtexture evolution and mechanical properties of a linear friction welded two-phase Ti-6.5Al-3.5Mo-1.5Zr-0.3Si titanium alloy joint were investigated. Results show clear microstructural differences at the joint center and edge. A martensitic and acicular α microstructure was found in the weld center zone (WCZ) at the joint center and a Widmanstatten microstructure can be identified in the WCZ at the joint edge. Further away from the WCZ, the microstructural differences smoothed out. The cross-weld crystallographic texture was assessed using electron back scattered diffraction. There are different α texture components in WCZ and thermomechanically-affected zone, but the β textures are similar in these two areas. The microstructural differences at the joint center and edge are the cause of the differences in microhardness distribution and tensile properties along the welding direction. Following post weld heat treatment, the inhomogeneity in both microstructure and mechanical properties were reduced.