Stress-assisted grain growth in nanocrystalline metals transpires collectively with a number of competing deformation mechanisms. In this study, molecular dynamics simulations of surface nanoindentation were performed to quantify the plastic strain distribution among competing mechanisms as a function of grain size and temperature during stress-assisted grain growth in nanocrystalline Ni and a Ni-1 at. % P alloy. Under identical conditions of rate and temperature in nominally the same grain size structure, stress-assisted grain growth found to be prevalent in pure nanocrystalline Ni was virtually absent in the Ni-P alloy with P enriched grain boundaries. A reduction in the deformation temperature also quelled mechanical grain growth in both nanocrystalline Ni, suggesting thermal activation was inherent to the governing physics. Plastic strain was found to be highly localized in the grain boundaries during nanoindentation, and dislocation activity while present, did not represent the dominant carrier of plasticity but an opponent factor against grain growth.
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