Evolution of structural and dynamic heterogeneities during elastic to plastic transition in metallic glass

Abstract

We investigate the evolution of microscopically localized flow under a constant applied strain in apparent elastic region of a prototypical metallic glass (MG). The distribution and evolution of energy barriers and relaxation time spectra of the activated flow units in MG with time are obtained via activation-relaxation method. The results show that the unstable nano-scale liquid-like regions acting as flow units in the glass can be activated by external stress, and their evolution with time shows a crossover from localized activation to cascade as the proportion of the flow units reaches a critical percolation value. The flow unit evolution leads to a mechanical elastic-to-plastic transition or macroscopic plastic flow. A plausible diagram involved in time, stress, and temperature is established to understand the deformations and the flow mechanisms of MGs and could provide insights on the intriguing dilemmas of glassy nature, the flow units, and their correlations with the deformation behaviors in MGs. V

Relaxation behavior of biaxially stretched PLA film during the heat setting stage

“…During the heat setting process, the deformation with the characteristic relaxation time less than the experimental time is involved in stress relaxation. On the contrary, the deformation that the characteristic relaxation time is greater than the experimental time does not participate in the relaxation (Zhao et al, 2015). Correspondingly, the flow unit has a critical energy activation.…”

“…Where σ 0 is the initial stress, and τ c is the characteristic relaxation time (Aval et al, 2020). The value of the extended exponential parameter β can reflect the dynamic inhomogeneity of the stress relaxation in the film, that is, the smaller β means the more significant dynamic inhomogeneity (Ediger, 2000;Zhao et al, 2015;Duan et al, 2022). The fitting curves for different stretching ratios are shown in Figure 5.…”