Influences of grain size and grain boundary segregation on mechanical behavior of nanocrystalline Ni

Nanocrystalline Ni with mean grain sizes ranging from similar to 15 to 95 nm was fabricated by electroplating and post-annealing. The influence of annealing on deformation behavior was systematically investigated by inspecting strain rate sensitivity (m) and activation Volume (V) using nanoindentation. In addition to the strong dependence of the Fit and V values on nanograin sizes, annealing induced grain boundary change, probably caused by GB relaxation and segregation, leads to the transition from a stress-activated dislocation emission mechanism in the as-fabricated sample to a thermal activation on dislocation emission. (C) 2009 Elsevier B.V. All Fights reserved.