Free volume gradient effect on mechanical properties of metallic glasses

Gradient of free volume distribution in metallic glasses is omnipresent either naturally or artificially in synthesis and application. But how the spatial inhomogeneity affects mechanical properties remains poorly understood. Here we probe this issue using finite element modeling. We find that the strength and toughness improves with increasing gradient; and the larger the gradient, the more effective. But the plasticity is marginally enhanced or even decreases. Too high the gradient value leads to brittle fracture caused by abrupt release of the large stress concentrated at the gradient region. The effects are represented in their relations with the gradient energy coefficient. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.