First-principles prediction of yield stress for basal slip in Mg–Al alloys |
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Authors: | GPM Leyson LG Hector WA Curtin |
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Affiliation: | 1. School of Engineering, Brown University, Providence, RI 02912, USA;2. General Motors Technical Center, 30500 Mound Road, Warren, MI 48090-9055, USA;3. Institute of Mechanical Engineering, Êcole Polytechnique Fédéral de Lausanne, Lausanne CH-1015, Switzerland |
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Abstract: | The finite-temperature yield stress of Mg–Al alloys undergoing basal slip is investigated using a recently developed parameter-free solute strengthening model. The model takes input from first-principles calculations of the dislocation/solute interaction energy and evaluates the solute strengthening due to fluctuations in solute concentration, taking into account the correlation of these fluctuations as a function of dislocation roughening. Due to the wide partial separation of the Mg basal edge dislocation, a smaller roughening is required to decorrelate the solute fluctuations in the partials compared to that required to decorrelate the fluctuations in the “far field”. As a consequence, the dislocation has two stable configurations in the random field of solutes, corresponding to “short-range” and “long-range” solute interactions. The configuration of the “short-range” interactions control the strength at low temperatures or high stress, whereas the “long-range” interactions control the strength at higher temperatures or lower stresses. Predictions of the model are in very good agreement with experiments over a wide range of solute concentrations and temperature. In particular, the model naturally predicts the “plateau stress” observed at high temperatures, which is attributable to the “long-range” solute interactions. |
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