Modification of atomic mobility in a Ti-based bulk metallic glass by plastic deformation or thermal annealing

Evolution of atomic mobility in a Ti ₄₀Zr ₂₅Ni ₈Cu ₉Be ₁₈ bulk metallic glass was studied by dynamic mechanical analysis (DMA) in different states: as-cast, after structural relaxation, after crystallization and after deformation (cold-rolled). Characteristics of Ti ₄₀Zr ₂₅Ni ₈Cu ₉Be ₁₈ bulk metallic glass are similar to that observed in other based bulk metallic glasses in the amorphous state: at low temperature, the material is mainly elastic and the mechanical response is independent of driving frequency, while on the other hand, the visco-elastic component becomes very large in the glass transition region. Structural relaxation and crystallization induce a decrease in the visco-elastic component, suggesting that atomic mobility is reduced. In contrast, atomic mobility is increased by a plastic deformation (i.e. cold-rolling). The higher is the cold-rolling ratio, the higher is the visco-elastic component. The experimental results were analyzed in the framework of quasi-point defects theory, which is based on the existence of defects in amorphous materials (polymer, bulk metallic glasses and other non-crystalline solids).