Grain refining efficiency and microstructure of Al–Ti–C–RE master alloy

Al–Ti–C–RE master alloy has been successfully prepared by reaction of K2TiF6 salt, graphite powder and rare earth (RE) with Al. The microstructure of the alloy was characterized by optical microscopy, X-ray diffraction, scanning electron microscopy equipped with energy-dispersive spectrometry. The results show the microstructure of Al–Ti–C–RE alloy is composed of α-Al, lath-shaped TiAl3, granular TiC, and blocky or rim Ti2Al20Ce. Compared with the Al–Ti–C master alloy, the addition of RE modifies the morphology of TiAl3 phase, accelerates the formation of TiC. Al–Ti–C–RE alloy was used for grain refinement studies on commercial pure aluminum. An excellent grain refining performance was obtained when the addition level of Al–Ti–C–RE reaches to 0.5 wt%. The refinement mechanism of Al–Ti–C–RE has also been discussed.

Research highlights▶ Using a melt reaction method, Al–Ti–C–RE master alloys with various amounts of RE were prepared. ▶ Investigating by optical microscopy, X-ray diffraction, scanning electron microscopy, and X-ray energy-dispersive spectrum, we discovered that the master alloy consisted of α-Al, lath-shaped TiAl3, granular TiC, and blocky or rim Ti2Al20Ce phases. ▶ We found that the addition of RE can promote the formation of TiC particle, modify the morphology and size of TiAl3 compound, as a result Al–Ti–C–RE master alloys showed a better grain refining performance than Al–Ti–C master alloys. ▶ The refinement mechanism of Al–Ti–C–RE has also been discussed.