Plastic dynamics transition between chaotic and self-organized critical states in a glassy metal via a multifractal intermediate

Abstract

Changes in intermittent serrated flow behavior during plastic deformation of Zr 64.13 Cu 15.75 Ni 10.12 Al 10 , a representative glassy metal with characteristic ductility, in response to variant strain rates and temperatures were examined. The influence of strain rates and environmental temperatures on the stress-time sequence of the plastic strain regime was investigated using comprehensive dynamical, statistical, and multifractal analyses. Three distinct spatiotemporal dynamical regimes were explored. Under small strain rates or high temperatures, the time-stress sequence exhibited a chaotic behavior. Conversely, under large strain rates or low temperatures, a transition to the self-organized critical (SOC) state was observed. In addition to chaotic time series and statistical analysis, multifractal analysis was also applied to study the crossover between these two unique plastic dynamic transitions. This plastic dynamical behavior was elucidated based on the interactions between shear avalanches in the glassy metal.

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

“…(1), the largest Lyapunov exponent implies an average exponentially diverging rate of the two trajectories in the phase space. 23 A positive Lyapunov exponent TABLE I. Mechanical properties of the metallic glass compressed at different temperatures.…”

The Self-Organized Critical Behavior in Pd-based Bulk Metallic Glass

“…Recently, the SOC behavior exhibits in serrated flow with the variation of the elastic energy during the plastic deformation [14]. The SOC behavior is a self-similar or scale-free pattern [19], i.e., the structures on one scale is almost the same with structures on the other scales.…”

“…The SOC behavior is a self-similar or scale-free pattern [19], i.e., the structures on one scale is almost the same with structures on the other scales. The transition of the plastic dynamics of the BMGs from a chaotic state finally to the SOC state is shown to correlate with different strain rates and temperatures [14]. To further investigate the SOC behavior of the serrated flows, the distribution of shear-avalanche sizes reflecting the shear avalanche in BMGs is discussed [27].…”

“…Sun et al [20] showed that the plastic deformation of ductile BMGs can evolve into a SOC state characterized by the power-law distribution of shear avalanches. Ren et al [14] found that the plastic dynamics of BMGs transition from a chaotic state to the SOC state are correlated with increasing strain rates and decreasing temperatures. In order to explore the serration dynamics in a Pd-based BMG, the amplitudes of serrations, compressive plasticity, as well as the SOC behavior of Pd75Si15Ag3Cu7 BMGs at different strain rates during serrated flows are investigated by statistical dynamical analysis.…”

“…The plastic deformation is a complex inhomogeneous process in the crystalline solids, and the dislocation motions are characterized by scale-free and intermittent avalanches [12], which are reminiscent of the concept of self-organized critical behavior (SOC) [13]. The SOC behavior is characterized by the continuous propagation of deformation bands near the upper strain rate boundary of plastic instability [14]. Although dislocation-mediated deformation mechanisms are absent in BMGs, the serrated flow phenomenon has been widely observed in compressive tests [15][16][17], which is associated with shear-band formation and propagation [18].…”