Boron-based refiners: Implications in conventional casting of Al-Si alloys

The effect of sole boron addition as inoculant has been studied in conventional casting of A356 alloy. It is shown that small addition of boron shifts up the cooling curve and makes the recalescence to disappear entirely. The columnar dendritic structure transforms to equiaxed morphology. For master alloys containing mainly AlB12 particles, it is proposed the dissolved boron, the AlB2 particles present in the master alloy, and some transformation of AlB12 to AlB2 are responsible for the enhanced refining. A hypothesis is proposed to clarify the role of the trace Ti on the nucleation of the primary α-Al particles