Bulk metallic glasses with large plasticity: Composition design from the structural perspective

While most bulk metallic glasses (BMGs) appear brittle at room temperature, appreciable compressive plastic strains have been observed for some glass compositions. The origin of this behavior is not understood, and the compositions of such plastic BMGs remain difficult to predict. Here we explain the plasticity observed in a Zr-Cu(Ni)-Al BMG, based on a computational analysis of the composition-dependent internal structures that influence shear transformations and shear localization behavior under loading. A strategy is then proposed to design BMG compositions with the desired local order for significant compressive plasticity, and is demonstrated by the successful discovery of an Hf₆₂Ni₂₅Al₁₃ BMG capable of sustaining large compressive strains. The experimentally measured compressive strength, glass transition temperature and Poisson's ratio, which are all composition dependent, are also shown to be macroscopic indicators that correlate well with the predictions from the atomic level structure.