Effect of Heterogeneous Deformation on Microstructure and Microtexture Evolution of Ti-6Al-4V Alloy during Multidirectional Isothermal Forging

The heterogeneous deformation of Ti-6Al-4V alloy during multidirectional isothermal forging and its effect on microstructure, microtexture, and related mechanical properties are investigated here. It is found that lowering the deformation temperature, combined with increasing the number of forging times, accelerates the grain refinement and recrystallization process in the as-received billet, especially in the surface section rather than the inner of the billet. Finally, a heterogeneous lamellar structure is formed after annealing the billet with a fourth step of forging. The heterogeneous lamella structure enables a better synergy of strength and ductility when compared to its equiaxed counterpart, achieving a high tensile strength of 1194 MPa and an elongation of 13.1%. During the deformation, a high proportion of back stress to total flow stress, ranging from 64-67%, denotes that back stress strengthening is one of the main reasons for the better synergy of strength and ductility. This study guides a low-cost and convenient way for the regulation of microstructure and mechanical properties of titanium alloy with good performance. For the strength and ductility trade-off in ultrafine-grained titanium alloys, in this study, a heterogeneous lamellar structure is constructed inside Ti-6Al-4V titanium alloy by controlling the forging and heat treatment parameters. The excellent comprehensive properties of heterogeneous lamella structure are mainly attributed to back stress hardening and fine grain strengthening.image (c) 2024 WILEY-VCH GmbH