Systematic research on thermal-deformation behavior and mechanism for a mono-phase near-β titanium alloy TC18

Thermal-deformation behavior and mechanism of a near-β titanium alloy TC18 in the mono-phase zone were studied by isothermal-compression experiments. The flow behavior of the alloy is predicted by an Arrhenius-constitutive equation considering strain. From the hot-working diagram, the unstable region primarily concentrates in high-strain-rate region, and is dominated by Deformation Bands (DBs) and Adiabatic Shear Bands (ASBs). The quantities of DBs and ASBs increase with temperature, and DB is the precursor of ASB. Obvious Dynamic Recovery (DRV), Discontinuous Dynamic Recrystallization (DDRX), and Continuous Dynamic Recrystallization (CDRX) exist in the stable region. The predominant microstructural evolution mechanisms at large strains shift from the synergistic effect of CDRX and DDRX below the inflection point temperature and at low strain rates, and the inhibitory effect of DDRX on CDRX above the inflection point temperature and at low strain rates, to the synergistic effect of both at medium strain rates, accompanied by enhanced DRV, and finally to DBs and ASBs at high strain rates. The main microtexture components for the deformed alloy are η bcc fiber, ε bcc fiber, α bcc fiber, γ bcc fiber, and ξ bcc fiber. The deformation microtexture is weakened owing to the stochastic orientation distribution of DRX grains.