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A General Criterion for Predicting the Activation of 〈c a〉 Dislocations in Magnesium Alloys

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Document pages: 22 pages

Abstract: The presence of alloying elements in magnesium (Mg) can activate pyramidal 〈c + a〉 slip systems and thereby improve the plasticity of Mg at room temperature. Several criteria for evaluating the activation of dislocations have been developed, but these often contradict experimental observations. Here, based on a synergistic effect stemming from both leading and trailing partial dislocations, we propose a more general and robust criterion - defined hereafter as "multiple energy barrier " (MEB) criterion - to predict the effect of alloying elements on the activation of 〈c + a〉 dislocations. Based on this proposed new criterion, we find that the addition of rare earths, Li, Ca, and Sn significantly lowers at least one energy barrier in pure Mg, and ultimately promotes the activation of the pyramidal I and or pyramidal II slip systems. The reduced energy barriers are mainly attributed to the local lattice distortions and charge redistribution induced by alloying atoms. These findings provide important insight into the influence of alloying on the activation of 〈c + a〉 dislocations, and may ultimately facilitate the development of a framework to design high-plasticity Mg alloys.

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