The present work has studied the recently developed Al Ti C B master alloy. Its microstructure and ability to grain refinement of commercial pure Al and Zr containing Al alloy were examined and compared with those of Al Ti B master alloy. The results show that there are Al 3Ti、 TiC and TiB 2 phases in Al Ti C B master alloy
which form small size、 dispersed multi phase clusters; the grain refining ability of Al Ti C B master alloy is superior to that of Al Ti B master alloy; It overcomes the shortcoming of Al Ti B master alloy poisoned by Zr atoms. It is thought that the excellent grain refining properties are attributed to the physical and chemical role of holes of multi phase clusters′ sufaces.