Effects of post-weld heat treatment on microstructure and properties of Ti180 electron beam welded joints

The study aimes to investigate the influence of heat treatment temperatures on the microstructure and mechanical properties of electron beam welded joints in the 7 mm thick Ti180 dual-phase titanium alloy. To achieve this, the different post-weld heat treatments (550−700 ℃, 8 h) were carried out on the welded joints. The results show that heat treatment leads to the formation of nano-scale needle-like α-phase and spherical submicron-particles Ti5Sn3 on the residual β-phase in the weld zone and heat-affected zone of the Ti180 electron beam welded joint. As the heat treatment temperature increases, the number of secondary acicular α' phases gradually decreases, the nanoscale acicular α phases gradually coarsen, and the spherical submicron particles gradually dissolve back into the matrix. Consequently, this results in a gradual decrease in the microhardness of the weld zone and heat-affected zone of the joints. The room-temperature tensile strength and elongation of the joint gradually decrease. However, there is an initial decrease followed by an increasing trend in the high-temperature tensile strength and elongation as the heat treatment temperature increase. Optimized mechanical properties of Ti180 welded joints is acquired at heat treatment parameters of 550 ℃, 8 h. And post-weld heat treatment plays a crucial role in reducing the residual stress of Ti180 welded joints. The optimum residual stress relief effect is achieved at a heat treatment temperature of 650 ℃. © 2023 Central South University of Technology. All rights reserved.