Unidirectional solidification of aluminium-nickel eutectic alloy

Abstract

Aluminium-nickel of (99.99 %) high purity eutectic alloy was melted in a graphite crucible under vacuum atmosphere. The eutectic alloy was directionally solidified upward with a constant growth rate, V (8.32 μm s-1) and different temperature gradients, G (0.83-4.02 K mm-1) and also with a constant G (4.02 K mm-1) and different V (8.32-483.25 μm s -1) in the Bridgman type directional solidification furnace. The eutectic spacings, λi, have been measured from both transverse section (λT) and longitudinal section (λL, λm and λM) of the specimens. The undercooling values Δ T were obtained by using V and system parameters K1, K2. It was found that the values of λi decreased while V and G were increasing. The relationships between eutectic spacing λi and solidification parameters G and V were obtained by linear regression analysis. The dependence of eutectic spacings λi (λT, λL, λm and λM) on undercooling (ΔT) were also analysed. λ2V, ΔTλ, ΔTV-0.5 and λ2G values were determined by using λi, ΔT, V and G values. The results obtained in this work were compared with the Jackson-Hunt eutectic theory and similar experimental works.