Direct quantification of solute effects on grain boundary motion by atomistic simulations

Direct quantification of grain boundary mobility with the presence of impurities poses a great challenge for investigating thermal stability of nanocrystalline alloys. By applying the interface random-walk method, we investigate the dopant segregation and precipitation from direct molecular dynamics simulations. It is found that existing atomistic simulation methods based on pure grain boundaries can be readily extended to extract the mobility of impure grain boundaries. Furthermore, it is confirmed that the grain boundary motion is controlled by the diffusion of segregated dopants at the interface as assumed by many theoretical models, but the grain boundary mobility is directly related to the impurity diffusion in the direction perpendicular to the boundary plane. By directly quantifying the mobility of impure grain boundary under experimental conditions, a correction to the well-accepted solute drag model is proposed.