Chemical misfit origin of solute strengthening in iron alloys

In this first-principles study, we investigate the effect of many kinds of substitutional solute species on screw dislocation motion in bcc-Fe, dominating the strength of dilute Fe alloys. Most of the solute species show a significant interaction with the dislocation core, while only several solute species among them, such as Si, P, and Cu, significantly lower the Peierls potential of the screw dislocation motion. A first-principles interaction energy with the “Easy-core” structure excellently correlates with the change in the γ-surface caused by solute atoms (i.e., chemical misfit). Based on the interaction energy, we predicted the effect of each species on macroscopic critical resolved shear stress (CRSS) of the dilute Fe alloy. The CRSS at low and high temperature for various alloys basically agree with experiment CRSS. These results provide a novel understanding of the interaction between a screw dislocation and solute species from the first-principles.

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