Aspect ratio effects on the serrated flow dynamic of TiZrHfCuNiBe high entropy metallic glass

Abstract

The effects of aspect ratio on serrated flow dynamic and plasticity of TiZrHfCuNiBe high entropy bulk metallic glass were investigated. With increasing of the aspect ratio, the stress drop time decreases and a ductile-to-brittle transition was observed, which indicates the motion of shear bands will berestricted in the specimens with smaller aspect ratio. Thus, the shear band velocity can be estimated based on the stick-slip dynamics, which enhances with increasing of the aspect ratio, while the critical shear band velocity is almost identical. Therefore, the specimens with larger aspect ratio will achieve the critical shear band velocity faster until fracture. When the aspect ratio is relatively small, the value of shear-band stability index is larger and promotes stable propagation of the shear bands. In addition, the plasticity and serration size are not monotonic correlated. Benefitting from the abundant secondary shear bands and the interactions at various scales, the plastic deformation can be regarded as the self-organized critical state for samples with better plasticity and lower aspect ratio. However, the self-organized critical state will switch to a chaotic state with increasing of the aspect ratio.