Microstructure Evolution and Mechanical Properties of Linear Friction Welded Ti-5Al-2Sn-2Zr-4Mo-4Cr (Ti17) Titanium Alloy Joints

The microstructural evolution, microhardness, tensile properties and impact toughness of Ti-5Al-2Sn-2Zr-4Mo-4Cr (Ti17) alloy joints welded by linear friction welding (LFW) are investigated. A narrow, sound weld is formed, consisting of a superfine alpha + beta structure in the weld center. The structure gradually changes from the weld center to the parent Ti17 in the TMAZ, with the highly deformed alpha and beta phases oriented along the deformation direction, owing to the uneven deformation and temperature distribution. The microhardness of the TMAZ is the lowest of the distinct zones and presents a valley-like shape. The tensile strengths of the joints are comparable to that of the parent Ti17 but with a much lower plasticity and impact toughness. The microstructure variation contributes to the resultant properties.