New insights into solidification and phase equilibria in the Al-Al3Zr system: Theoretical and experimental investigations

Abstract

Phase equilibria and phase transformations during the solidification of alloys in the Al-Al3Zr corner of the Al-Zr system were investigated using both theoretical (DFT and Calphad modelling) and experimental techniques. This work involved two separate teams investigating the phase transformations of alloys of different compositions during solidification at slow cooling rates using DTA, SEM, TEM, XRD, EPMA analysis of as-cast and annealed samples. The formation of eutectic type colonies at the boundaries of dendrites and three types of primary intermetallic phase crystals were detected in the examined samples. A eutectic reaction was implied from the results of a DTA analysis. The obtained results question the currently accepted phase diagram for this part of the system which was based on measurements of the solubility of Zr in the aluminium solid solution and the liquidus surface.