Flaw-induced plastic-flow dynamics in bulk metallic glasses under tension

Abstract

Inheriting amorphous atomic structures without crystalline lattices, bulk metallic glasses (BMGs) are known to have superior mechanical properties, such as high strength approaching the ideal value, but are susceptible to catastrophic failures. Understanding the plastic-flow dynamics of BMGs is important for achieving stable plastic flow in order to avoid catastrophic failures, especially under tension, where almost all BMGs demonstrate limited plastic flow with catastrophic failure. Previous findings have shown that the plastic flow of BMGs displays critical dynamics under compression tests, however, the plastic-flow dynamics under tension are still unknown. Here we report that power-law critical dynamics can also be achieved in the plastic flow of tensile BMGs by introducing flaws. Differing from the plastic flow under compression, the flaw-induced plastic flow under tension shows an upward trend in the amplitudes of the load drops with time, resulting in a stable plastic-flow stage with a power-law distribution of the load drop. We found that the flaw-induced plastic flow resulted from the stress gradients around the notch roots, and the stable plastic-flow stage increased with the increase of the stress concentration factor ahead of the notch root. The findings are potentially useful for predicting and avoiding the catastrophic failures in tensile BMGs by tailoring the complex stress fields in practical structural-applications.

Study On The Cutting Performance of High-Speed Machining Zr-Based Bulk Metallic Glass

“…As a new kind of metallic materials, BMGs have unique mechanical and physical properties and a wide range of application prospects [24][25][26]. Although the strength of Zr57 BMG is high, the main cutting force is relatively small, as compared with conventional Zr702.…”

Deformation Behavior of Bulk Metallic Glasses and High Entropy Alloys under Complex Stress Fields: A Review

“…By laser surface melting, gradient distribution of both tensile and compressive residual stresses as well as atomic structural changes can also be employed to improve the macroscopic plasticity of BMGs [ 74 , 75 ]. In addition, Wang et al [ 76 ] have obtained an obvious enhancement in the tensile plasticity of BMGs by surface mechanical attrition treatment. Gradient atomic structures were formed during the mechanical attrition process, resulting in a gradient distribution of residual stress with both compressive and tensile stresses.…”

“…Thereafter, by tailoring single-side notches with varying radii, complex stress fields with varying stress concentration factors have been introduced to some tensile BMG specimens [ 76 ]. Despite different trends in the evolution of amplitudes from compression tests, the flow serrations of the single-side notched BMG specimens also demonstrate power-law criticality within the stable plastic flow stages, similar to the results under compression and nano-indentation tests [ 76 ]. The power-law criticality in BMGs might be a universal rule for all kinds of loading conditions.…”

“…Gradient atomic structures were formed during the mechanical attrition process, resulting in a gradient distribution of residual stress with both compressive and tensile stresses. They have shown that the gradient distribution of residual stress can cause the formation of more shear bands, and at the same time, delay the cavitation effect, resulting in a work-hardening mechanism associated with enhanced plasticity [76]. bands, but also influence the propagation of shear bands, even under simple gradient stress distributions.…”

On the variation of the mechanical energy accumulation rates during the flow serrations of a Zr-based bulk metallic glass

“…At room temperature, the plastic deformation of BMGs is highly localized in thin layers of shear bands, demonstrating serrated plastic flows in the stress-strain curves [8,9]. The formation of the serrations is significantly affected by the applied strain rates [10][11][12] and external disturbances, such as the geometric confinement [9,13] and stress gradients [14][15][16]. For example, Schuh et al showed that with increasing loading rates, the plastic deformation in BMGs transits from serrated flows into homogeneous deformation [11].…”