Effect of cold deformation and heat treatment on microstructure and mechanical properties of TC21 Ti alloy

In the present research work on TC21 titanium alloy (6.5Al−3Mo−1.9Nb−2.2Sn−2.2Zr−1.5Cr), the effects of cold deformation, solution treatment with different cooling rates and then aging on microstructure, hardness and wear property were investigated. A cold deformation at room temperature with 15% reduction in height was applied on annealed samples. The samples were solution-treated at 920 °C for 15 min followed by different cooling rates of water quenching (WQ), air cooling (AC) and furnace cooling (FC) to room temperature. Finally, the samples were aged at 590 °C for 4 h. Secondary α-platelets precipitated in residual β-phase in the case of solution-treated samples with AC condition and aged ones. The maximum hardness of HV 470 was obtained for WQ + aging condition due to the presence of high amount of residual β-matrix (69%), while the minimum hardness of HV 328 was reported for FC condition. Aging process after solution treatment can considerably enhance the wear property and this enhancement can reach up to about 122% by applying aging after WQ compared with the annealed samples. © 2020 The Nonferrous Metals Society of China