Effects of normal stresses on the homogeneous nucleation of a basal dislocation in magnesium

A quantitative evaluation of the deformation of metals is usually based on the critical resolved shear stress (CRSS), in which the influence of the normal stresses is not taken into account. Although it is plausible to use the CRSS for a quantitative evaluation of the deformation mode, some previous studies show that the CRSS depends on other stress components. In this work, atomistic simulations are performed to study the influence of the normal stresses on the nucleation of basal dislocations in a magnesium single crystal. We found that the activation free energy of dislocation nucleation decreases as the normal stress applied in the [112¯0] direction decreases, or that in the [0001] direction increases. This tendency is consistent with the dependence of CRSS on the loading direction found in a previous work done by Barrett et al. (2012) on molecular dynamics simulations of tensile deformation tests of a magnesium single crystal.

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