Shear-Band Deformation in Amorphous Alloys and Composites

The deformation of monolithic bulk-metallic glasses (BMGs), nanocrystal-containing, and micrometer-sized, ductile-particle-reinforced bulk metallic glass composites (BMGCs) has been investigated. The number density of shear bands, the interaction of shear bands with the particles, as well as the apparent plasticity was found to be significantly different in three types of samples before failure occurred. The interaction of shear bands with the micrometer-sized particles implied that shear bands can be initiated by stress concentration at the particle boundaries and, at the same time, absorbed by the deformation of particles. It is hypothesized that the observed number density and motion of shear bands could arise from the interaction of rotational sliding of medium range order (MRO) or dense-packed clusters, fine crystals, and the free volume in the material. An estimate of the shear band thickness, based on the size of particles or grains near and in the shear bands of the BMGs, BMGCs, and ultra-fine structured materials is consistent with this conjecture.