Molecular dynamics simulations of grain size stabilization in nanocrystalline materials by addition of dopants

Molecular dynamics simulations of bulk nanocrystalline Cu with dopant atoms segregated in the grain boundary regions were performed to investigate the impediment to grain growth caused by the dopants during annealing at constant temperature of 800 K. In this parametric study, the concentration and atomic radii mismatch between the dopants and the host atoms were systematically varied to determine how to most effectively retard grain growth. It is found that samples with positive excess enthalpy (ΔH) underwent various degrees of grain growth; however, when ΔH was negative, no coarsening occurred. Also, ΔH varied linearly with dopant concentration with the slope equal to the enthalpy of segregation, in agreement with previous theoretical work.