Microstructure and phase forming process of Al-3Ti-0.2C-1RE grain refiner

An Al-3Ti-0.2C-1RE grain refiner was prepared by in-situ reaction method. The microstructure was investigated by optical microscopy (OM), scanning electron microscopy (SEM) equipped with energy-dispersive spectrometry (EDS) and X-ray diffraction (XRD). The results show that the Al-3Ti-0.2C-1RE grain refiner is composed of α-Al, TiAl3, TiC and Ti2Al20Ce phases. Compared with Al-3Ti-0.2C refiner, the morphology of TiAl3 phase is changed and Ti2Al20Ce phases form with the addition of RE. Accordingly, the refining performance is improved. The phase forming process of the refiner is as follows: Blocky Ti2Al20Ce and fine blocky TiAl3 form in the melt at the initial stage of reaction, then the fine blocky TiAl3 gradually disappears, and the blocky Ti2Al20Ce grows bigger with the increase of holding time. The predominant mechanism to synthesize TiC particles is the reaction between high concentration of solute Ti atoms and graphite particles.