Atom probe tomography of GB segregation in nanocrystalline Ni alloy

In this study, atom probe tomography was employed to investigate atomic-scale element distributions in an electroplated nanocrystalline Ni alloy. Quantitative characterization evidences that weak yet detectable grain boundary segregations of carbon and cobalt occur during low-temperature electroplating. Nanoindentation measurements suggest that the hardness of the alloy is ~1 GPa higher than that of the nanocrystalline pure Ni with the same grain size. Classical solid solution strengthening cannot completely account for the hardness increment and hence the grain boundary segregations appear to play an important role in the strength improvement.