Chemical bonding effects on the brittle-to-ductile transition in metallic glasses

F Moitzi and D Sopu and D Holec and D Perera and N Mousseau and J Eckert, ACTA MATERIALIA, 188, 273-281 (2020).

DOI: 10.1016/j.actamat.2020.02.002

The influence of composition and temperature on the tensile deformation behavior of amorphous PdSi metal-metalloid alloys is investigated using large-scale molecular dynamics simulations. A correlation between highly directional Si-Si bonds and the deformation mechanisms is revealed by a Crystal Orbital Hamilton Population analysis based on electronic structure calculations from density functional theory. A transition from cracking perpendicular to the loading direction to shear banding can be achieved by increasing the temperature or decreasing the amount of silicon. Sampling of the saddle points on the potential energy surface reveals that a high fraction of rigid covalent Si-Si bonds increases the energy barriers for atomic rearrangements. These thermally-activated atomic relaxation events change the stress and strain state in the elastic regime and are precursor of local plasticity. High activation energies impede both the stress and the strain redistribution and cause cleavage-like cracking due to a delay of the onset of plasticity. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

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