Directional and rapid solidification of Al–Nb–Ni ternary eutectic alloy

Abstract

Al–Nb–Ni alloy system exhibits ternary eutectic transformation during solidification, resulting in in situ Al3Nb–Nb2Al–AlNbNi composite material. This paper investigates the influence of the cooling rate on the solidification microstructure of the eutectic Al–Nb–Ni alloy, under equilibrium and non-equilibrium solidification conditions. Al57.2Nb40.4Ni2.4 eutectic alloy was directionally solidified using the Bridgman method and also rapidly solidified by melt-spinning process. The samples were characterized by scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. Solidification with lower growth rate resulted in eutectic structure consisting of three solid phases in very regular arrangement, with fibrous morphology. However, solidification with very high growth rates resulted in a very refined and irregular eutectic, revealing changes in the eutectic morphology from rod-type to eutectic cell and supersaturated structures.