Improving strain hardening capacity of high-strength Ti–6Al–4V alloy by a dual harmonic structure

Abstract

By TiH2/Al60V40 powder processing, in-situ dehydrogenation, and powder compact extrusion, we successfully fabricate a Ti–6Al–4V (wt.%) alloy with a dual harmonic structure. Such multilevel structural heterogeneity is attained by suppressing the stabilization effect of the residual hydrogen on β-Ti phase, through controlling the prior β grain sizes and interstitial element contents. It is demonstrated that this dual harmonic structure is beneficial in alleviating mechanical mismatch between hetero-domains and fully exploiting the hetero-deformation induced hardening, thereby leading to a high strain hardening rate and large uniform elongation. As a result, the material exhibits a better strength-ductility synergy (an ultimate tensile strength of 1338 MPa and a uniform elongation of 7.7%) than both the one-level harmonic and homogeneously structured materials. The present ‘tailoring structural heterogeneity through manipulating hydrogen-enabled eutectoid transformation’ strategy offers a different pathway to design and fabricate novel heterogeneously structured titanium alloys with a high strength-ductility synergy.