Effect of Plate Thickness on Tensile Property of Ti–6Al–4V Alloy Joint Friction Stir Welded Below β-Transus Temperature

Defect-free joint of Ti–6Al–4V alloy was successfully friction stir welded below β-transus temperature and then tensile tests were performed. Microstructure, macrostructure, tensile properties and fracture position are mainly discussed in order to investigate how surface indentation and plate thickness influence the tensile property. Weld zone (WZ) attained below β-transus temperature that owns better tensile strength limit than base metal (BM). During the tensile test, the elongation is decided by whether BM yields. Compared with friction stir welding joint using 2.5 mm thick plate, it is very difficult for joint using 2 mm thick plates to get bigger elongation due to surface indentation. Due to the higher tensile property of the WZ, the joint without surface indentation fractures at BM, reaching the 58.46 % elongation of BM.