In this paper, we successfully produced Al-Ti-B-C master alloys through adding mixtures of Ti and B4C powders into Al melt. XRD and SEM examinations suggest that only fine TiB2 and TiC particles are formed in the matrix of Al-Ti-B-C master alloy when the Ti/B4C molar ratio is 3/1, while an additional TiAl3 phase is present when the Ti/B4C molar ratio exceeds 3/1. The produced Al-Ti-B-C master alloys exhibited high grain refinement effect for pure Al. It was found that the presence of TiAl3 phase in the matrix of Al-Ti-B-C master alloy enhanced the grain refinement efficiency and the mechanism was discussed.

An Al-Ti-N master alloy was prepared through the addition of AlN and Ti powders into pure Al melt heated in an induction furnace. This master alloy shows a higher grain refinement effect for pure Al than Al-Ti due to the formation of TiN and/or AlxTiyNz particles in the Al matrix. DTA, SEM and XRD results suggest that TiN and/or AlxTiyNz particles start to form at about 970°C during heating the Al-Ti-AlN powder mixture.

In this paper, two types of Zn-Al-Ti-C master alloy with different Ti/C ratios were produced throug a two-step method, characterized by XRD and SEM, and their refinement behaviors and mechanism in Zn-50Al alloy were studied. Both of the master alloys remarkably reduced the size of α-Al grains, impeded the dendritic growth and promote the equiaxed growth of α-Al grains in Zn-50wt.%Al alloy. The master alloy containing both TiC and dditional Ti in the Zn-Al matrix was found to have higher refinement ability than that containg only TiC. The refinement effect of both master alloys was greatly enhanced as the solidification temperature of Zn-50Al melt decreases. TiC particles were observed to be located at the center of α-Al grains and act as the nucleating substrate for α-Al. The decrease of melt solidification temperature and the presence of additional Ti atoms in the Zn-50Al melt cause higher melt supercooling, which further elevate the nucleating rate of α-Al grains on TiC particles and promote the equiaxed growth of α-Al grains.