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.