Exceptionally high strain-hardening and ductility due to transformation induced plasticity effect in Ti-rich high-entropy alloys

Abstract

Ti-rich body-centered cubic (BCC, β) high-entropy alloys having compositions Ti₃₅Zr_27.5Hf_27.5Nb₅Ta₅, Ti₃₈Zr₂₅Hf₂₅Ta₁₀Sn₂, and Ti₃₈Zr₂₅Hf₂₅Ta₇Sn₅ (in at%) were designed using bond order (Bo)-mean d-orbital energy level (Md) approach. Deformation mechanisms of these alloys were studied using tensile deformation. The alloys showed exceptionally high strain-hardening and ductility. For instance, the alloys showed at least twofold increment of tensile strength compared to the yield strength, due to strain-hardening. Post-deformation microstructural observations confirmed the transformation of β to hexagonal close packed (HCP, α') martensite. Based on microstructural investigation, stress-strain behaviors were explained using transformation induced plasticity effect. Crystallographic analysis indicated transformation of β to α' showed strong variant selection (1 1 0)_β//(0 0 0 1)_α', and [1 - 1 1]_β//[1 1 - 2 0]_α'.