Effect of heat treatment on microstructure and hardness of Ti₂AlNb linear friction welding joint

Linear friction welding (LFW) test and post-weld heat treatment of welded joints of Ti₂AlNb alloy were carried out. The microstructure evolution in recrystallization zone and thermo-mechanical affected zone of Ti₂AlNb LFW joint with post heat treatment were analyzed. The results showed that high quality joint of Ti₂AlNb without microcrack and microvoid could be formed by LFW. WZ (weld zone) consisted of metastable β phase and few of twisted α₂. TMAZ was made of O phase, metastable β phase and much of twisted α₂ phase. After heat treatment, metastable β broke down into O lamina precipitate and the size of O lamina increased with the temperature from 700 °C to 900 °C. Microhardness increased obviously after heat treatment at 700 °C while it decreased with the increasing of temperature.