Directional solidification studies in complex ternary alloy systems

Abstract

Directional solidification of ternary melts in a series of Al-based systems (Al–Co–Cu, Al–Co–Ni, and Al–Cu–Fe) has been studied using the Bridgman technique at a very low growth rate. These systems have been chosen to investigate the phase equilibria of quasicrystals and structurally complex crystalline compounds in the vicinity of quasicrystal-forming composition regions. The Bridgman-grown ingots were characterized by optical microscopy, electron microprobe analysis, powder X-ray diffraction, and differential thermal analysis. Using this combination, it was possible to study phase equilibria and crystallization processes with respect to the liquidus surface projection. The solidification paths for the ternary quasicrystal-forming alloys and structurally complex crystalline phases traced in the Bridgman-grown specimens have been discussed within the framework of the Scheil–Gulliver solidification model. It has been proved that the Bridgman method is a feasible tool to study the complex solidification processes of ternary alloys.