Glass formation by severe plastic deformation of crystalline Cu vertical bar Zr nano-layers

SZ Li and L Pastewka and P Gumbsch, ACTA MATERIALIA, 165, 577-586 (2019).

DOI: 10.1016/j.actamat.2018.11.045

We use molecular dynamics simulation to study the formation of glasses during severe plastic deformation of crystalline Cu vertical bar Zr nano-layers in a simple shear geometry. The early stage of plasticity is governed by dislocation plasticity. Dislocation-interface interaction induces interface roughening and slow atomic-level intermixing around interfaces. A solid-state crystal-to-amorphous transition starts near the interfaces. At high strain, the interfaces are refined to merge, leading to the formation of an intermixed glassy zone that eventually spans our simulation cell. Dislocation emission is then suppressed and strain is fully accommodated by this glassy phase. We characterize the crystal-to-amorphous transition using local structural measures, such as the pair distribution function and Voronoi analysis. The onset of glass formation occurs at a critical shear strain that increases with layer thickness. Our simulations indicate that the parameter controlling this onset is the theoretical affine interface distance, i.e. the amorphization occurs at a critical value of around 3-4 nm that increases slightly with the increase of layer thickness. Our work provides insights on mechanically driven glass formation in multicomponent systems, as e.g. realized in ball-mills or high-pressure torsion experiments. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

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