Nanoindentation creep of nanocrystalline nickel at elevated temperatures

Abstract

Nanoindentation creep of nanocrystalline Ni with the as-deposited grain size of 14 nm was characterized at elevated temperatures. The indentation creep rate was observed to scale with temperature and applied load, and could be expressed by an empirical equation used for describing power-law creep in conventional crystalline solids. Creep activation energy was found to be close to that for the grain boundary self-diffusion of Ni. The activation volume was also measured using a stress relaxation technique. The current creep results were directly compared with those from fine-structured Ni in the literature. Possible creep mechanisms, such as diffusional creep, grain boundary sliding, power-law and power-law breakdown, were discussed in light of the creep rate and temperature ranges.