Coupling effect of deformation temperature and strain rate on mechanical properties in TWIP Ti-15Mo alloy

Both deformation temperature and strain rate affect the mechanical properties of β titanium alloy, and are related to the change of deformation mode in the process of plastic deformation. The effects of deformation temperature and strain rate coupling on the mechanical properties of {332}〈113〉 twinning induced plastic effect Ti-15Mo alloy were studied by TEM, EBSD, SEM, XRD, OM and tensile testing machine.The results show that as increase of strain rate, yield strength increases at 298 K and 573 K, which is intensively dependent on dislocation thermal activation behavior. The larger contribution of dislocation activation at 573 K exhibites the higher strain rate dependency on yield strength. At 573 K, the Ti-15Mo alloy is deformed by {332}〈113〉 twinning and dislocation slip, which is different from that at 298 K, and the established flow stress model indicates that dislocation strengthening has a greater contribution. At a high strain rate, the formation of more twins at early deformation suppresses the subsequent formation of twins, decreasing the work hardening rate, whereas can effectively decrease the local stress concentration due to the inhomogeneous distribution of dislocations, delaying the necking. Consequently, these two factors result in the lower strain rate dependency on flow stress in the Ti-15Mo alloy under the coupling effect of deformation temperature and strain rate.