Enhancing Creep Resistance of Powder-Metallurgy Near-β Titanium Alloy via Rapid Heat Treatment Followed by Aging

In this work, rapid heat treatment followed by aging (RHTA) was proposed to improve the creep properties of Ti-5Al-5Mo-5 V-1Cr-1Fe alloy produced by sintering and hot deformation of blended elemental powder compacts. At 400  °C., the stress exponents of alloy after annealing and RHTA are 2.66 and 3.05. At the stress of 300 MPa with temperatures in the range of 400-500  °C., the activation energies of alloy after annealing and RHTA are 192.1 kJ/mol and 223.0 kJ/mol, respectively. The stress exponents and activation energies indicate that the creep in specimens after annealing and RHTA was mainly affected by dislocation climb, which has been proved by the jogged screw dislocations observed by TEM. The fine α lamellae obtained by RHTA contributed to the evidently better creep resistance than that of the alloy with equiaxed structure after hot rolling and annealing. Importantly, the results confirmed that the bimodal microstructure obtained by RHTA can achieve better creep resistance than full lamellae structure obtained by traditional heat treatment.