Approaching the universal yield point of bulk metallic glasses from molecular dynamics simulations

Shimizu, Futoshi ; Ogata, Shigenobu*; Kaburaki, Hideo; Li, J.*

Most bulk metallic glasses (BMG) yield at about 2% strain in uniaxialtension/compression test. A careful analysis of the elementary shearbehavior in contrast to crystalline concepts such the generalized stacking fault (GSF) energy reveal a particularly simple and direct explanation. We perform molecular dynamics (MD) simulations on 2-component model systems and a 5-component BMG system, observing and characterizing the nucleation and evolution of shear bands. Despite gross uncertainties in the interatomic interactions and the pre-deformation glass structure, our MD results give a reasonable account of the 2% universal yield point. The general concepts of glass rejuvenation and aging, which we call alienation and recovery process in the context of intense localized shear, and occurring mainly within a timescale of 1-100 atomic vibration periods, is postulated to play acritical role. This theory (various points has also been proposed byothers) can explain why the yield point is relatively insensitive to the interatomic potential and the structure of the pre-deformed glass.