Kinetic Properties of Triple Junctions in Metals Studied by Atomistic Simulations

Abstract

Nanocrystalline materials could exhibit high mechanical yield strength. Nevertheless, with a high volume fraction in nanocrystalline material, grain boundaries and triple junctions which store a relatively high free energy, are thermally instable which potentially contribute to grain growth. On the other hand, since both grain boundaries and triple junctions are prior sites of impurity enrichment which could in return reduce the triple junction energy, alloys with impurity enriched in grain boundaries and triple junctions are widely applied to stabilize the nanostructures. However, past studies mainly focused on grain boundaries and the kinetic properties of triple junctions and their influences on the thermal stability of nanocrystalline metals is less studied. In this work, triple junction mobility and impurity diffusivity in triple junction are studied by molecular dynamics simulations. Specifically, interface random walk method due to thermal fluctuation which has been widely applied to extract grain boundary mobility is extended to study triple junction motion.