Microstructure and deformation mechanisms in nanocrystalline Ni-Fe. Part II. In situ testing during X-ray diffraction

Deformation mechanisms in nanocrystalline electrodeposited Ni (26 nm) and Ni-Fe (12 nm) are studied by strain rate sensitivity experiments and in situ mechanical testing during X-ray diffraction. We find a relatively low strength for Ni-Fe, which may be ascribed to a weakening of dislocation pinning points. Furthermore, the strain rate sensitivity of Ni-Fe is relatively low. The in situ studies allow the macroscopic mechanical response of Ni to be divided into three different deformation regimes: elastic, microplastic and macroplastic. For Ni-Fe, recovery mechanisms seem particularly important, resulting in an extended microplastic regime and necking before a state of homogeneous deformation can be reached. (C) 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.