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 X-ray 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.