Microstructure and properties of the linear friction welded joints between the different quality TC17 with post-weld aging treatments

Linear friction welding has been a key technology for manufacturing aero-engine blisks. The microstructure and properties of linear friction welded (LFW) joints of TC17 (α + β) and TC17(β) titanium alloy and post weld aging treatment (PWAT) joints at different temperature are compared by testing of optical microscope, scanning electron microscope, universal testing machine and microhardness tester. The results show that the microstructure of the weld and the surrounding area in the welded state is supercooled β-fine grained, with the lowest hardness. After post-weld aging treatment, fine needle-like α-phase is precipitated, and the hardness increases. The hardness values of the welding area and the surrounding area are obviously increased when the post-weld aging temperature is 400 ℃, and the welding area is embrittled. The bending angle of the joint is the highest, but the strength decreases when the post-weld aging temperature is 630 ℃. With the considerations of both the bending and tensile properties of the welded joint, the optimal post-weld aging temperature is found to be 550 ℃. The joint’s bending angle and tensile strength could reach 36% and 95% of that of the base metal, respectively. The micro plasticity deformations of TC17(α + β) thermal and mechanical affected zone (TMAZ) are more uniform after applying force, and its strength and plastic properties are than those of the TC17(β) side TMAZ. The weakest zone of the joint is located at TC17(β) TMAZ, where the variations of the hardness and microstructure have the greatest gradient. Compared with the base metal, the plastic loss of LFW joint is much greater than the strength loss.