Microstructures and mechanical properties of hot-press sintered bulk nanocrystalline nickel

In order to explore the practical preparation method of bulk nanocrystalline nickels, direct current arc plasma evaporation method and hot-press sintering are used to prepare the bulk nanocrysta-lline nickels under lower temperatures. The crystal structures, surface micrographs and porosities of nickels are studied by employing the X-ray diffraction(XRD), transmission electron microscope(TEM), scanning electron microscope(SEM)and Archimedes method. The compressive properties of the specimens at ambient temperature are also investigated by using the digital image correlation method(DIC). The results show that the bulk nanocrystalline nickel with an average grain size of 62.1 nm can be prepared by sintering under 2.5 GPa and 500°C. This sample has a relative density of 95.8%, an ultimate tensile strength of 905 MPa, an elongation to failure of 11.5% and no obvious yield. However, its plasticity decreases due to narrow grain size distribution and the holes in the bulk nanocrystalline nickels.