Post-annealing effect on the tensile deformation mechanism of a Ti-6Al-4V alloy manufactured via directed energy deposition

Abstract

Although the post-annealing of additively manufactured materials is an important process in obtaining reliable mechanical properties, it is still not comprehensively understood how the annealing conditions affect the microstructural evolution and mechanical properties of an additively manufactured Ti-6Al-4V alloy. In this study, the effect of post-annealing on the mechanical properties exhibited by a direct energy deposition processed Ti-6Al-4V alloy was investigated by subjecting samples of the alloy to varying annealing conditions and tensile testing temperatures. Depending on the annealing temperature, post-annealing can induce microstructural changes, including lath growth, local misorientation relief, and prior 8 grain transition, each of which contribute to the strength reduction and ductility increase observed during the tensile test. The tensile testing temperature affects the slip system activity observed in the Ti-6Al-4V alloy; as the temperature increases, the critical resolved shear stress is reduced. Based on the prismatic and basal slip system activation, a significant strain hardening capability and ductility were observed in the tensile deformed Ti-6Al-4V at elevated temperatures. This result alludes to the detailed deformation mechanisms exhibited by the additively manufactured and post-annealed Ti-6Al-4V, which can then be used to optimize the properties exhibited by metallic products through the application of post-treatments.