Stress Relaxation and Diffusion in Zr-Based Metallic Glasses Having Wide Supercooled Liquid Regions

Abstract

We investigated the stress relaxation behavior and diffusion of Zr-Al-Ni-Cu metallic glasses having a wide supercooled liquid region. The stress relaxation was more pronounced after yielding and its relaxation rate increased with temperature. The stress relaxation was associated with the stress overshoot that is a transient stress-strain phenomenon. The stress overshoot appeared again after the stress relaxation in the course of stretch, and increased with an increase in stress relaxation fraction. The glassy structure appears to change into a state with higher atomic mobility by yielding, and to return its initial structure by the stress relaxation. The temperature dependence of the diffusivity in the supercooled liquid phase above the glass transition temperature was significantly different from that in the amorphous phase. The activation energy for diffusion in the supercooled liquid phase was much larger than that in amorphous phase below the glass transition temperature.