Nanovoid failure in Magnesium under dynamic loads

C Gregoire and M Ponga, ACTA MATERIALIA, 134, 360-374 (2017).

DOI: 10.1016/j.actamat.2017.05.016

The dynamic behavior of Magnesium (Mg) single crystals containing nano- sized voids and the mechanisms responsible for failure under different loading conditions are studied by means of Molecular Dynamics (MD) simulations. Our study reveals that the response is highly anisotropic leading to a brittle to ductile transition in the failure modes under different load orientations. This transition is accompanied by different mechanisms of deformation and is associated with the anisotropic Hexagonal Close Packed (HCP) lattice structure of Mg and the associated barrier for dislocation motion. Remarkably, brittle failure is observed when external loads produce a high stress triaxiality while the response is more ductile when the stress triaxiality decreases. The fundamental mechanisms observed in the simulations, therefore, explain the low spall strength of Mg and suggest the possibility of manipulating some mechanisms to increase ductility and spall strength of new lightweight Mg alloys. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

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