Structural heterogeneity induced plasticity in bulk metallic glasses: From well-relaxed fragile glass to metal-like behavior

Abstract

To reveal the structural origin responsible for the sharp change of the fracture mode on the as-cast and thermally-relaxed status, we use nanomechanical testing to measure the stresses for the onset of plasticity of a metallic glass and develop a stochastic statistical model, which can be used to characterize structural heterogeneity (defect density and strength) inside the metallic glass. Our experiments and calculations found that, with increasing the structural relaxation, the defect density drops by two orders of magnitude. Correspondingly, the fracture of metallic glasses changes from a significantly plastic (metal-like) mode to an extremely brittle (fragile glass) one.