A comparison of the refining effect between Al 3%Ti 3%B and Al 5%Ti 1%B master alloys for hypoeutectic Al Si alloys has been made. Experimental results indicated that Al 3%Ti 3%B master alloy has a stronger grain refining effect than Al 5%Ti 1%B master alloy. After addition of Al 5%Ti 1%B master alloy to Al Si alloy melts

excessive Ti on the Ti B 2/melt interface forms a ternary Al Ti Si compound which acts as heter geneous nudeifor α Al during peritectic reaction

But the decrease of peritectic temperature reduction grain refinement; When Al 3%Ti 3%B is added to aluminum melt

excessive B on the TiB 2/melt refines grain by homogeneous nuclei during eutectic rection.