Thermal stability up to 800 °C of a Ni–4 wt% Al nanocomposite

Abstract

The thermal stability up to 800 °C of a nanocrystalline (NC) Ni (mean grain size ~25 nm) with ~4 wt% Al dispersed in the form of ~160-nm-sized particles, which was fabricated by co-electrodeposition from a nickel sulfate bath, has been investigated using differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results showed that microstructural evolution of the composite is temperature dependent, i.e., normal grain growth of the NC Ni, ~0.6 wt% Al solution into the Ni matrix and direct reaction between Al and Ni to form Ni3Al precipitates occurred at ~290, ~325 and ~575 °C, respectively. The distribution of Al in Ni matrix with temperature is fully discussed. A DSC scanning up to 800 °C of a nanocrystalline Ni matrix dispersing ~4 wt% Al particles (mean size: 160 nm) shows the particles did not significantly affect the normal grain growth of NC Ni and they have been converted into Ni3Al and Al solute atoms.