Serration Dynamics in a Zr-Based Bulk Metallic Glass

Abstract

Intermittent or serrated plastic flows have been widely observed in irreversible deformation through shear banding in bulk metallic glasses (BMGs). The strain-rate-dependent plasticity under uniaxial compression at 2 9 10 À3 , 2 9 10 À4 , and 2 9 10 À5 s À1 in a Zr-based BMG is investigated. Serration events have a typical time scale at a relatively higher strain rate (2 9 10 À3 s À1 ), while at lower strain rates, there is a lack of typical time scale. During serrations, the stress is falling rapidly, and the amplitude of the stress drop between the neighboring serrations is approximately equal. The stress drop vs time satisfies the exponential decay rule during jerk flows. Due to the serrated flow corresponding to the internal shear process, the freevolume model and stick-slip model are introduced to explain how the shear bands form and propagate and the cooperation of multiple shear bands. The mechanism is explained by relating the atomic-scale deformation with the macroscopic shear-band behavior, offering key ingredients to fundamentally cognize serrations in jerk flows.

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

“…It is obvious that the yielding strengths are almost the same value of 1650 MPa, and the compressive plasticity keeps similar values about ~6% at different strain rates. The repeating cycles of a sudden stress drop are followed by reloading elastically, which accord with the previous results [23][24][25]. In order to eliminate the machine vibration error, any serration event with a stress fluctuation less than 5 MPa in jerky flows is excluded in the present statistical analysis.…”

Serration behaviours in metallic glasses with different plasticity

“…Such results indicate that a pure SOC behaviour might not be the only option for MGs plasticity. Some other studies also have shown that the plasticity could also be achieved with a serration pattern in peak distribution [17,18]. Some studies suggest that the shear band dynamics in plastic MGs could also be understood by a tuned criticality behaviour instead of the SOC behaviour [16].…”

“…Some statistics studies reveal that the shear bands follow a self-organised critical (SOC) behaviour or chaotic KEYWORD Metallic glass; shear band; plasticity; serration ARTICLE HISTORY behaviour in MGs with different plasticity, where the serration pattern falls in a power law distribution or peak distribution [10,11,15]. However, there are also contradictory reports showing different serration patterns and shear band dynamics in plastic MGs [16][17][18]. Then, it is important to reveal the origin of the different plasticity in MGs, and the relationship among serration pattern, shear band dynamics and plasticity of MGs.…”

Metallic glass matrix composites

“…More comprehensive mechanisms are expected. For example, very recently, we have unveiled an exponential decay of shearing stresses with the time or strain during serrations in BMGs [253,262]. The flow stresses with the time satisfy the following relation: c is the heat capacity, T r is room temperature, T g is the glass-transition temperature, E is the Young's modulus of BMGs, and a is the aspect ratio of the tested samples.…”