Universality of plastic instability and mechanical yield in metallic glasses

The generic response of a wide range of amorphous solids is the average increase of stress upon external loading until the yielding transition point, after which elasto-plastic steady state sets in. The stress–strain response comprises of a series of elastic branches interspersed with plastic drops. The ubiquitousness of these phenomena indicates universality, independent of material property, but the literature predominantly deals with specific materials. In pursuit of generality among different amorphous systems, we undertake a careful investigation in the mechanical response of metallic glasses using computer simulation. By comparing our results of multi-body metallic glass potentials to those obtained from pairwise Lennard-Jones glasses, we show that the mechanism of plastic instabilities is universal and independent of the details of the underlying potential. We also investigate the yielding transition in terms of the overlap parameter Q ₁₂, which has been successfully used Lennard-Jones glasses. The yielding is unambiguously identified as a first-order phase transition. These observations conform the nature of plastic instabilities and mechanical yield as universal and independent of microscopic interactions. (paper)