Effect of Annealing on Microstructure and Tensile Properties of Ti-6.5Al-2Sn-4Zr-2Mo-2Nb-1W-0.2Si Alloy

The effects of single annealing on microstructure and mechanical properties of an (α+β) high-temperature titanium alloy (Ti-6.5Al-2Sn-4Zr-2Mo-2Nb-1W-0.2Si) were studied by optical microscopy (OM), scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and tensile testing. The results showed that with annealing temperature increasing the volume fraction of primary α phase decreased gradually, while the volume fractions of transformed β structure and secondary α phase increased, and the sizes of these phases became coarse. Elevating the annealing temperature, the room temperature strength didn't change at first and then decreased, the high temperature strength increased gradually, and the ultimate tensile strength and yield strength at 650°C can reach more than 700 MPa and 500 MPa, respectively. Meanwhile, both room temperature and high temperature ductility decreased with the annealing temperature increasing. In order to acquire good strength at high temperature and plasticity at room temperature, the best single annealing temperature is 980°C.