Effect of solution treatment and aging on microstructure, tensile properties and creep behavior of a hot-rolled β high strength titanium alloy with a composition of Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe-0.1B-0.1C

Microstructure, tensile properties and creep behavior of a hot-rolled beta high strength Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe-0.1B-0.1C alloy were investigated in the present study. The alloy was heat treated along different regimes to study the effect of heat treatments on microstructure evolution, tensile and creep properties. After solution treated at 830 degrees C and aged at 300 degrees C, 560 degrees C successively, the microstructure yielded equiaxed beta grains and acicular secondary alpha phase with small size because of assisted-nucleation effect of omega phase and pseudo-spinodal mechanism. The alloy had the highest strength of both ultimate tensile strength (1508 MPa) and yield strength (1440 MPa). And all the specimens treated along different regimes manifested the features of combined fracture mechanism with the existence of ductile dimples and cleavage surfaces. After creep deformation for 100 h, the alloy solution treated and aged at 560 degrees C had the lowest steady-stage creep rate and minimal creep strain of 3.9%. In addition, during the heat treatments, some equiaxed alpha phase precipitated abnormally and dissolved into beta matrix during the creep deformation. The phenomenon can be attributed to the differences of diffusion ability among different compositions, which resulted in the appearance of composition fluctuation and non-equilibrium precipitation.