Real-time observation of grain nucleation and growth during solidification of aluminium alloys

The crystallisation kinetics of liquid aluminium-titanium alloys with microscopic TiB2 particles added to refine the grain size in the solidified material was studied by Xray diffraction measurements at a synchrotron source. Real-time observation of the formation and growth of individual grains reveals the central role played by the added TiB2 particles during solidification. Prior to the main transformation, weak reflections of a metastable TiAl3 phase were detected. This observation finally pinpoints the highly debated mechanism responsible for enhanced grain nucleation in Al-Ti-B alloys.