Unraveling the threshold stress of structural rejuvenation of metallic glasses via thermo-mechanical creep

The competition between physical aging and structural rejuvenation determines the physical and mechanical properties of glassy materials. Thus, the rejuvenation-aging boundary must be identified quantitatively. In this work, we unravel a stress boundary to distinguish rejuvenation from aging via the thermo-mechanical creep of a typical Zr-based metallic glass. The crept glasses were rejuvenated into high-enthalpy disordered states when the applied stress exceeded a threshold that was numerically close to the steady-state flow stress; otherwise, the glasses were aged. A theoretical model for glass creep was adopted to demystify the observed stress threshold of rejuvenation. The model revealed that the thermo-mechanical creep beyond the threshold stress could activate sufficient shear transformations to create a net free volume, thus leading to structural rejuvenation. Furthermore, we derived the analytical expressions for the threshold and flow stresses. Both stresses can act as the rejuvenation-aging boundary, which is well supported by experimental creep data. The present work procures a deeper understanding of the rejuvenation mechanism of glasses and provides useful implications for abstaining from glass aging.

Automated summary

The stress boundary between rejuvenation and aging in glassy materials was identified through thermo-mechanical creep experiments. When the applied stress exceeded a threshold, the glass could be rejuvenated into a high-enthalpy disordered state, otherwise it aged. A theoretical model explained the observed stress threshold and showed that creep beyond the threshold stress could lead to structural rejuvenation by creating a net free volume. The derived analytical expressions for the threshold and flow stresses were validated with experimental data, providing useful implications for preventing glass aging.