Ab initio and atomistic study of generalized stacking fault energies in Mg and Mg-Y alloys
Z Pei and LF Zhu and M Friak and S Sandlobes and J von Pezold and HW Sheng and CP Race and S Zaefferer and B Svendsen and D Raabe and J Neugebauer, NEW JOURNAL OF PHYSICS, 15, 043020 (2013).
Magnesium-yttrium alloys show significantly improved room temperature ductility when compared with pure Mg. We study this interesting phenomenon theoretically at the atomic scale employing quantum- mechanical (so-called ab initio) and atomistic modeling methods. Specifically, we have calculated generalized stacking fault energies for five slip systems in both elemental magnesium (Mg) and Mg-Y alloys using (i) density functional theory and (ii) a set of embedded-atom-method (EAM) potentials. These calculations predict that the addition of yttrium results in a reduction in the unstable stacking fault energy of basal slip systems. Specifically in the case of an I-2 stacking fault, the predicted reduction of the stacking fault energy due to Y atoms was verified by experimental measurements. We find a similar reduction for the stable stacking fault energy of the 11 (2) over bar2< 11 (2) over bar3 > non-basal slip system. On the other hand, other energies along this particular gamma-surface profile increase with the addition of Y. In parallel to our quantum-mechanical calculations, we have also developed a new EAM Mg-Y potential and thoroughly tested its performance. The comparison of quantum-mechanical and atomistic results indicates that the new potential is suitable for future large-scale atomistic simulations.
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