Measurements of the microhardness, electrical and thermal properties of the Al–Ni eutectic alloy

Al–5.7 wt% Ni eutectic alloy was directionally solidified upward with different temperature gradients (0.83–4.02 K/mm) at a constant growth rate (0.008 mm/s) and with different growth rates (0.008–0.483 mm/s) at a constant temperature gradient (4.02 K/mm). Microhardness (HV) and electrical resistivity (ρ) of directionally solidified samples were measured using microhardness test device and a standard d.c. four-point probe technique, respectively. Dependency of the microhardness and electrical resistivity on the solidification processing parameters (temperature gradient, G and growth rate, (V) were analyzed. According to these results, it has been found that the values of HV and ρ increase with the increasing values of G and V. Variations of electrical resistivity and electrical conductivity (σ) for casting Al–Ni eutectic alloy were also measured at the temperature in range 300–720 K. The enthalpy of fusion (ΔH) for the Al–Ni eutectic alloy was determined by differential scanning calorimeter (DSC) from heating trace during the transformation from solid to liquid.