Shear banding instability in \remove{high entropy} multi-component metallic glasses: Interplay of composition and short-range order}

TL;DR

This study uses atomistic simulations to explore how composition and short-range order influence shear banding and strain localization in multi-component metallic glasses, revealing that increased icosahedral ordering promotes more homogeneous deformation.

Contribution

It demonstrates the interplay between composition-driven icosahedral ordering and shear transformation zones in controlling shear banding in metallic glasses, highlighting new insights into the structural factors affecting plasticity.

Findings

Strain localization varies from diffuse to crack-like with composition changes.

Higher icosahedral ordering correlates with strain delocalization.

Plastic yielding can be predicted by compositional descriptors like the misfit parameter .

Abstract

The shear-banding instability in quasi-statically driven bulk metallic glasses emerges from collective dynamics, mediated by shear transformation zones and associated non-local elastic interactions. It is also phenomenologically known that sharp structural features of shear bands are typically correlated to the sharpness of the plastic yielding transition, being predominant in commonly studied alloys composed of multiple different elements, that have very different atomic radii. However, in the opposite limit \remove{of high-entropy multicomponent alloys,} where elements' radii are relatively similar, plastic yielding of bulk metallic glasses is highly dependent on compositional and ordering features. In particular, a known mechanism at play involves the formation of short-range order dominated by icosahedra-based clusters. Here, we report on atomistic simulations of multi-component metallic glasses with different chemical compositions showing that the degree of strain localization is largely controlled by the interplay between composition-driven icosahedra-ordering and collectively-driven shear transformation zones. By altering compositions, strain localization ranges from diffuse homogenized patterns to singular crack-like features. We quantify the dynamical yielding transition by measuring the atoms' susceptibility to plastic rearrangements, strongly correlated to the local atomic structure. We find that the abundance of short-range ordering of icosahedra within rearranging zones increases glassy materials' capacity to delocalize strain. The kind of plastic yielding can be often qualitatively inferred by the commonly used compositional descriptor that characterizes element associations, the misfit parameter $\delta_a$, and also by uncommon ones, such as shear-band width and shear-band dynamics' correlation parameters.