Abstract
Multi-principal element alloys (MPEAs) continue to attract considerable attention. However, one fundamental question regarding their plasticity remains far from well understood, namely, how the nanoscale heterogeneity and chemical short-range order (SRO) control dislocation motion and plasticity. Different from previous studies incorporating statistical variations of the energy landscape into full dislocation dynamics, the current work proposes an innovative atomistically informed partial dislocation dynamics (PDD) method, which directly considers the spatially-correlated non-uniform planar fault energy (PFE) at the atomic scale, and at the same time benefits from the larger temporal and spatial scales of the dislocation dynamics methods. Through systematic analysis, we find that the PFE field exhibits a negative correlation along the atomic slip direction, which reduces the critical stress required for dislocation motion in that direction. In contrast, the correlation characteristics along other directions can be approximated as uncorrelated noise, which also contributes to strengthening. In addition, it is found that SRO only slightly enhances the correlation strength along certain crystallographic directions, while it weakens the degree of negative correlation along the slip direction. Overall, the increase in the mean PFE induced by SRO significantly contributes to the strengthening of the dislocation depinning transition. The proposed model provides new opportunities for designing MPEAs with tailored macroscopic mechanical properties by manipulating their atomic distribution and spatial correlations.
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