Anelastic-like nature of the rejuvenation of metallic glasses by cryogenic thermal cycling

Cryogenic thermal cycling (CTC) is an effective treatment for improving the room-temperature plasticity and toughness in metallic glasses. Despite considerable attention to characterizing the effects of CTC, they remain poorly understood. A prominent example is that, contrary to expectation, the stored energy in a metallic glass first rises, and then decreases, as CTC progresses. In this work, CTC is applied to bulk metallic glasses based on Pd, Pt, Ti, or Zr. The effects on calorimetric and mechanical properties are evaluated. Critically, CTC-induced effects, at whatever stage, are found to decay over about one week at room temperature after CTC, returning the properties to those of the as-cast glass. A model is proposed for CTC-induced effects, treating them as analogous to the accumulation of anelastic strain. The implications for analysis of existing data, and for future research on CTC effects, are highlighted.

Automated summary

Cryogenic thermal cycling (CTC) is an effective method to improve the room-temperature plasticity and toughness of metallic glasses. However, the effects of CTC are still not well understood, especially the unexpected behavior of stored energy in metallic glasses during CTC. This study applies CTC to bulk metallic glasses based on Pd, Pt, Ti, or Zr, and evaluates the effects on calorimetric and mechanical properties. The results show that the CTC-induced effects decay over time and the properties return to their original state. A model is proposed to explain the CTC-induced effects as the accumulation of anelastic strain. The implications for data analysis and future research on CTC effects are highlighted.