Characteristics of stress relaxation kinetics of La₆₀Ni₁₅Al₂₅ bulk metallic glass

Abstract The β relaxation typically plays an important role in the plastic deformation of glassy materials. Compared with amorphous polymers, most of the metallic glasses do not show evident β relaxation based on mechanical spectroscopy. However, La₆₀Ni₁₅Al₂₅ bulk metallic glass (BMG) exhibits a prominent β relaxation process, which could be an ideal model alloy to investigate the correlation between the β relaxation and mechanical behavior of metallic glasses. In this work, compressive properties and stress relaxation at high temperature (below glass transition temperature T_g) were studied. Stress relaxation of La₆₀Ni₁₅Al₂₅ BMG was measured by uniaxial compressive tests and mechanical spectroscopy around both α and β relaxation temperature domain. At higher temperatures and sufficiently low strain rate, the flow behavior of the La₆₀Ni₁₅Al₂₅ BMG could be simulated by a master curve, showing that the behavior is independent of temperature, especially on the proximity of the β relaxation process. Because the existence of the β relaxation, a high value of the activation volume for the plastic deformation could be ascribed to the existence of a specific atomic arrangement in the La₆₀Ni₁₅Al₂₅ BMG. It is found that compressive stress relaxation kinetics parameter remains temperature independent below T_g.