Correlation between High Temperature Deformation and β Relaxation in LaCeBased Metallic Glass.

Hightemperature deformation around the glass transition temperature T and the dynamic mechanical behavior of LaCeAlCo metallic glass were investigated. According to dynamic mechanical analysis (DMA) results, LaCeAlCo metallic glass exhibits a pronounced slow β relaxation process. In parallel, strainrate jump experiments around the glass transition temperature were performed in a wide range of strain rate ranges. The apparent viscosity shows a strong dependence on temperature and strain rate, which reflects the transition from nonNewtonian to Newtonian flow. At low strain or high temperature, a transition was observed from a nonNewtonian viscous flow to Newtonian viscous flow. It was found that the activation volume during plastic deformation of LaCeAlCo metallic glass is higher than that of other metallic glasses. Higher values of activation volume in LaCeAlCo metallic glass may be attributed to existence of a pronounced slow β relaxation. It is reasonable to conclude that slow β relaxation in LaCeAlCo metallic glass corresponds to the "soft" regions (structural heterogeneities) in metallic glass.