Hydrogen-induced softening in nanocrystalline Ni investigated by nanoindentation

The influence of hydrogen on the plastic deformation of nanocrystalline nickel was analysed by recourse to nanoindentation on the uncharged and hydrogen-charged samples. It was revealed that, in nanocrystalline Ni, hydrogen significantly decreases hardness but does not alter the strain rate sensitivity. Through thermal desorption spectroscopy measurement, charged hydrogen was expected to reside in face-centred cubic lattice, grain boundaries (GBs) and vacancies rather than dislocations. The hydrogen-induced softening behaviour is discussed in terms of the possible roles of hydrogen in GB-assisted dislocation flow mechanism.The work at Hanyang University was supported in part by the National Research Foundation of Korea (NRF) grant funded by the Korea Government (MSIP) [grant number 2013R1A1A2A10058551]; the Human Resources Development program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korea Government (MOTIE) [grant number 20134030200360]. The work at KIST was supported by the Convergence Agenda Program (CAP) of the Korea Research Council of Fundamental Science and Technology