Microstructure and mechanical properties of inertia friction welded joint of Ti-22Al-25Nb alloy

The Ti-22Al-25Nb alloy was welded by inertia friction welded technology. The microstructure and microhardness of welded joints before and after heat treatment were studied. The tensile mechanical properties at 650 degrees C and 750 degrees C of welded joints were analyzed. The results show that the weld zone of the as-welded joint consists of B2 phase and a very small amount of residual a z phase. After heat treatment, the weld zone consists of B2 phase and O phase. The O phase is transformed from B2 phase, and there is no composition change during the phase transition process. The microhardness of the as-welded zone is higher than that of the base material. After heat treatment at 780 degrees C for 3 h, the microhardness of the welded zone increases significantly due to the precipitation of fine O phase. But the microhardness of the welded zone with heat treatment at 800 degrees C for 3 h is between that of the as-welded state and the heat treatment at 780 degrees C for 3 h. The specimen of high temperature tensile fracture in the base material, and the tensile fracture morphology presents ductile fracture feature with many small shallow dimples.