Temperature dependent dynamics transition of intermittent plastic flow in a metallic glass. II. Dynamics analysis

Abstract

By reducing the testing temperatures down to the temperature well below the glassy transition temperature, the serrated flow behaviour during plastic deformation of a Zr-based metallic glass was experimentally investigated and the results were presented in Part I of the present paper. It shows that the yield strength, the plastic deformation ability, the density of shear bands of the metallic glass increase with decreasing temperature. In order to understand the mechanisms for the changes of the mechanical behaviour at low temperatures, in Part II of this study, the stress-time sequence in the plastic strain regime is characterized by a comprehensive dynamical and statistical analysis. The stress-time sequence is found to exhibit a chaotic state at high temperatures (>203 K), whereas a self-organized critical state is obtained at low temperatures ( 203 K) due to the freezing effect. The reasons for the transition between these two distinct spatio-temporal dynamical states are elucidated by investigating the effect of temperature on the deformation units (shear transformation zones) and the elastic interactions between neighbouring shear bands. The results demonstrate that the low temperatures results in an enhancement of the interactions between the elastic strain fields initiated by neighbouring shear bands, which is primarily responsible for the enhanced plasticity of the metallic glass and a dynamics transition. V C 2013 AIP Publishing LLC.

Correlation between atomic structure evolution and strength in a bulk metallic glass at cryogenic temperature

“…A bond reorientation model was deduced to describe the anisotropic structural evolution in BMGs2829, suggesting that the atomic rearrangements in the first nearest neighbor shell initiate a concordant shift of the surrounding atoms. Along this line, a concordant shifting region is developed, and treated as the primary deformation units to deliver the plastic strain303132. Our in-situ X-ray diffraction results upon cooling corroborate that expansion in the first nearest neighbor shell happens, which is attributed to the changes in the local structure of the polyhedra or in the atomic arrangement in the short-range order33.…”

Dynamic properties of major shear bands in Zr–Cu–Al bulk metallic glasses

“…a cumulative size distribution which follows a power law, has been reported for BMG serrations. The respective studies, however, did not consider in depth the impact of the degree of geometric constraints on these distributions [25][26][27][28].…”

The mechanism of power-law scaling behavior by controlling shear bands in bulk metallic glass

“…It is found that shear avalanches could present a power-law scaling behavior [28,35]. The power-law scaling behavior has a significant feature that the internal state is a self-similar or scalefree pattern, i.e., the structures on one scale are almost the same as structures on the other scales.…”