Influence of parent metal microstructure and post-weld heat treatment on microstructure and mechanical properties of linear friction welded Ti-6Al-4V joint

Linear friction welding (LFW) of Ti-6Al-4V (Ti-64) titanium alloy with a different microstructure from the previous study was conducted. The joint microstructure, tensile strength and fracture characteristics were studied. Results show that the microstructure of parent metal has a strong influence on the microstructure and properties of LFW Ti-64 joints. Under the specific conditions in this study, unexpected spheric α grains were formed near the bondline, which leads to the steep drop of the joint tensile strength. Although the tensile strength could be improved through post-weld heat treatment, the failure of specimens still took place across the bondline with the cleavage fracture due to the formation of basket-weave structure at the weld center zone and the remaining of spheric α grains.