A scheme for achieving strength-ductility trade-off in metallic glasses

Abstract

The strength-ductility paradox in structural materials remains a long-standing dilemma in advanced materials synthesis. Metallic glasses (MGs) that are structural materials of remarkably high-strengths are not exclusive in structural applications due to their inherently poor plasticity. This study addresses this conundrum by presenting a scheme for achieving excellent strength-ductility synergy in MGs from structural and energetic standpoints. By applying a two-step pathway of mechanical rejuvenation and cyclic stress loadings upon a Zr2Cu as-constructed MG model, deformation behavior was analyzed by molecular dynamics simulations. As higher energy states of the MG characterized by enhanced compressive plasticity was found by mechanical rejuvenation due to internal stress accumulation accompanied with an unusual increase in free volume and atomic energy, cyclic stress loading upon rejuvenation annihilated loosely-packed regions to advance a more stable state with less energy to enhance structural stability with an improvement in elastic strain limit and strength. By theoretical modelling, strength-ductility trade-off was demonstrated by the delay in shear transformation zone activities that orchestrated the generation and intersection of multiple shear bands. As a result, a two-step scheme in which soft regions are aggregated to a concentered mass intensified to higher potential energy followed by dissipating the consolidated mass into randomly dispersed soft regions is the key to achieve the strength-ductility trade-off in MG materials. The outcome of this study will further advance structure-property characterization in amorphous solids.