Microstructure and formation mechanism of grain-refining particles in Al-Ti-C-RE grain refiners

The Al-5Ti-0.2C-based grain refiners with different contents of rare earth (RE) were successfully prepared via powder metallurgy and vacuum casting. The microstructural evolution has been studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that the RE addition resulted in the formation of TiAl3/Ti2Al20RE core-shell structured primary particles, and the size of TiAl3 core decreased, while the thickness of Ti2Al20RE increased with increase of RE contents. As compared to Al-5Ti-0.2C grain refiner, the grain refining efficiency was gradually improved with increase of RE contents, which was mainly attributed to the TiAl3/Ti2Al20RE core-shell structured primary particles and insoluble TiC nuclei formed in a-Al matrix. The formation mechanism of core-shell structure was further investigated based on Ginstling-Brounstein model.

SEM images and line scan elemental profiles across the primary particle of Al-5Ti-0.2C-3.0RE (a, b)Figure optionsDownload as PowerPoint slide