The modification of the primary silicon in hypereutectic Al-20wt.% Si alloy by boron has been investigated. The results show that boron addition can obviously modify the primary silicon in hypereutectic Al-20wt.% Si alloy. The size of the primary silicon decrease with the increase of boron addition content from 0 to 0.065 wt.%

and the minimum size of the primary silicon can be obtained at the boron addition content of 0.065 wt.%. But

the size of primary silicon increases if the boron addition content is continuously increased after the boron content of 0.065%