Investigation of edge dislocation mobility in Ni-Co solid solutions by molecular dynamics simulation

The mobility of edge dislocations in Ni-based solid solutions with a wide range of Co concentration was investigated by performing molecular dynamics simulations at different temperatures and shear stress levels. The results reveal that the resistance to dislocation motion increases with Co content and temperature, whereas at high Co content the effect of temperature diminishes. By analyzing the simulation results in conjunction with the dislocation mobility model, we find that the solute effect differs at different concentrations. At low Co content, the solute atoms influence the dislocation motion primarily by regulating the lattice misfit and elastic misfit, in line with the solid solution strengthening theory. While at high Co content, they also affect the dislocation motion via modification to the lattice vibrations, in addition to the solid solution strengthening effect. It turns out that the dislocation mobility model and the classical solid solution strengthening model agree well with each other in describing the composition dependent critical stress required for dislocation motion.