Atomistic study on effects of solute atoms on energy profile of edge dislocation mobility in FCC-Cu alloys

Solid-solution strengthening is an effective method to increase the mechanical strength of metal alloys. Revealing the solid-solution strengthening mechanism based on the energy profile of the dislocation motion is vital for the non-empirical development of high-strength metal alloys. This study provides detailed energy profiles (i.e., energy surfaces) of the edge dislocation gliding motion under the effect of solute atoms, as well as the atomic-scale origin of solute strengthening in face-centered cubic (FCC) Cu alloys. The maximum shear stress (τmax) required for the dislocation to leave the solute atoms (Ni, Co, and Mo, all with different sizes and stacking fault effects) was qualitatively evaluated by finite temperature molecular dynamics simulations. By the nudged elastic band (NEB) analysis, we determined the atomistic origin of the energy barrier for the edge dislocation motion and the maximum force required to overcome the solute pinning effect (i.e., depinning force, FNEB) in binary Cu alloys. By linking FNEB to the size misfit, a theoretical prediction model based on size effects and the volumetric strain field was used and can qualitatively explain the increment in the maximum shear stress (Δτmax) by the solute atoms. These results provide an atomistic basis for the prediction of the solute-strengthening effect correlated with the edge dislocation motion in wide FCC systems.