Grain refining in hypoeutectic AlSi casting alloys has become an essential practice of melt treatment. The grain refinement with three types of master alloys: binary AlTi

binary AlB

and ternary AlTiB with Ti or B in excess of the TiB2 stoichiometry

in hypoeutectic AlSi casting alloys was different from that in commercial purity aluminum and its wrought aluminum alloys. Al3Ti3B and Al3B master alloys exhibited very excellent grain refining ability in hypoeutectic AlSi casting alloys and the interaction between Si and grain refiners was thought to play an important role during grain refinement. The quality of melt treatment in AlSi alloy could be controlled by evaluating and predicting the grain refinement and modification with differential thermal analysis equipment. There are four grain refinement mechanisms in hypoeutectic AlSi casting alloys: peritectic reaction theory

eutectic reaction theory

boride particles theory

and hypernucleation theory. The recent development of grain refining

intera