Facile Route to Implement Transformation Strengthening in Lightweight Alloys

Abstract

Developing lighter, stronger and more ductile aerospace metallic materials is in demand for energy efficiency strategies. Alloys with twinning-induced plasticity (TWIP) and/or transformation-induced plasticity (TRIP) effects have been exploited to defeat the conflict of strength versus ductility, yet very few if any physically informed methods exist to address the complex interactions between transitions. Here we report a facile route to deploy transformation-mediated strengthening in lightweight Ti alloys, which particularly focuses on the controlled activation of TRIP and TWIP via a mechanism-driven modelling approach. New alloys were comparatively developed and presented notable resistances to strain localisation, but interestingly through distinct mechanical characteristics. Specifically, extraordinary strain-hardening rate with a peak value of 2.4 GPa was achieved in Ti-10Mo-5Nb (wt.%), resulting from the synergetic activation of hierarchical transformations. A model integrating TRIP and TWIP was applied to understand the interplays between the transition mechanisms that individually contribute to strength and uniform elongation.