EFFECT OF CRYSTALLIZATION AND SURFACE TREATMENT ON DEFORMATION AND FRACTURE OF Zr-Ti-Cu-Ni-Be BULK METALLIC GLASS

Abstract

In this study, the cracking behavior in the bulk and the stress-strain responses of partially crystallized Zr - Ti - Cu - Ni - Be bulk metallic glass after surface modification were investigated. The compressive plasticity was found to be dependent on the surface conditions. The plasticity was enhanced significantly by a complete removal of visible surface flaws. The electro-plating of copper on the rough surface also increased the plasticity of Zr base BMG of the present study. The beneficial effect of the electro-plating can be attributed to filling and smoothening effect due to plating and/or the ductilization of the surface, both of which does not favor crack nucleation. We also found the cracking behavior in the bulk different from the surface region. The cracks in the center of the sample were not straight, but wavy, suggesting the cracks were deflected by or attracted to crystalline particles. A high magnification view of a crack revealed small triangular shaped crystals along the crack path.