Phase Evolution in Hypereutectic Al90Cu10-xNix (x=0, 5) Alloys

The present work is aimed at understanding the phase evolution of hypereutectic Al-rich Al-Cu-Ni in situ composites consisting of ultrafine eutectic with micron scale dendrites. The hypereutectic Al90Cu10-xNix (x = 0, 5) are synthesized by vacuum arc melting technique under high purity argon atmosphere. Detailed X-ray diffraction and electron microscopic (SEM and TEM coupled with EDS) studies have been carried out to identify the phases in these alloys. Thermodynamic calculations performed using CALPHAD approach using ThermoCalc(A (R)) software predict the equilibrium solidification path. The Al90Cu5Ni5 alloy exhibits ternary quasi-peritectic reaction of L + Al3Ni -> (Al)(ss) + Al3Ni2 at invariant point, which is supported by two univariant reactions i.e. L + Al3Ni -> Al3Ni2 and L -> (Al)(ss) + Al3Ni2 above and below the invariant point respectively.