Microstructural heterogeneity evolution of Zr-based bulk metallic glass during nanoindentation creep

The creep behavior and micro-mechanisms of Zr41.2Ti13.8Cu12.5Ni10Be22.5 bulk metallic glass (Zr-BMG) were investigated at room temperature using nanoindentation technology under different loading rates and peak loads (holding loads). The creep stress was calculated using the work-of-indentation, the creep stress-time curve was fitted and analyzed by combining the Kohlrausch-Williams-Watts (KWW) equation, the activation volume formula, and the generalized Maxwell model, revealing the dynamic evolution of microstructural heterogeneity, flow units, relaxation time spectra, and activation energy spectra. The results show that as the peak load and loading rate increase, the stress drop magnitude increases, exhibiting a typical stress relaxation phenomenon. The activation energy is closely related to the internal microstructural heterogeneity, the more significant the microstructural heterogeneity, the lower the required activation energy, making flow units more easily activated. This study provides important experimental evidence and theoretical support for a deeper understanding of the creep behavior and micro-mechanical mechanisms of metallic glass.