Abnormal grain coarsening mechanism in conical nickel

The abnormal grain coarsening frequently occurs in nanocrystalline metals during the process of plastic deformation. However, the origin of the abnormal grain coarsening at atomic scale for a wide range of strain and temperature remains unexplored. Here, the dynamic abnormal-grain-growth behavior is investigated experimentally. The abnormal grain coarsening of conical nickel substrate under the compressive deformation is studied using molecular dynamics (MD) simulations. The results show that the temperature can control the evolution process of dislocation and grain boundary under gradient strain fields, and then dominates the grain coarsening. The strain-dominated grain coarsening is found at nanoscale, and relies on the gradient strain, which can activate the nucleation of dislocation, dissociation of grain boundary and deformation twinning.