Physical and mechanical properties of Al-Si-Ni eutectic alloy

Al-11.1wt%Si-4.2wt%Ni alloy was directionally solidified upward under different conditions, with different growth rates (V=4.60-243.33 mu m/s) at a constant temperature gradient (G=5.82 K/mm) and with different temperature gradients (G=2.11-5.82 K/mm) at a constant growth rate (V=11.63 mu m/s) by using a Bridgman type directional solidification furnace. The microstructure of directionally solidified Al-11.1wt%Si-4.2wt%Ni alloy was observed to be irregular plates of Al3Ni and Si within an alpha-Al matrix from quenched samples. The microhardness, tensile strength and electrical resistivity of the alloy were measured from directionally solidified samples. The dependency of the microhardness, tensile strength and electrical resistivity for directionally solidified Al-Si-Ni eutectic alloy on the solidification parameters were investigated and the relationships between them were experimentally obtained by using regression analysis. Additionally, the variation of electrical resistivity with temperature in the range of 300-825 K for the Al-Si-Ni eutectic cast alloy was also measured using a standard d.c. four-point probe technique. The enthalpy of fusion and specific heat for the same alloy were determined by a differential scanning calorimeter from the heating curve during the transformation from eutectic solid to eutectic liquid. The results obtained in the present work were compared with previous similar experimental results.