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

2015 
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.
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