Anelastic and viscoplastic deformation in a Fe-based metallic glass

Abstract The micro-creep behavior of the Fe66Tb5B23Nb6 metallic glass and its anelastic and viscoplastic deformation mechanism were investigated by using nanoindentation. The Maxwell-Voigt model with one or two Kelvin units were utilized to describe three stages of creep deformations at different loading rates and temperatures during the constant load holding process. The creep displacement of the indenter into the Fe66Tb5B23Nb6 sample at a constant load obeys the classic relaxation kinetics at loading rates ranging from 5 to 100 mN s−1. The activation energy for the relaxation process increases with increasing loading rate, which leads to the pronounced relaxation with longer characteristic times under a low-velocity impact mode observed at room temperature. On the other hand, the relaxation process with a short characteristic time plays a dominant role in determining viscoplastic flow and softening behavior at the temperature approaching the glass transition temperature. This work reveals the important role of the anelasticity on the plastic flow of metallic glasses under dynamic loading conditions.