Effects of combinative addition of lanthanum and boron on grain refinement of Al–Si casting alloys

•α-Al grains in Al–2Si alloy can be refined by the combinative addition of La and B.•The addition of La can eliminate the mutual poisoning between Sr and B.•The addition of La benefits the tensile properties, especially the elongation.

In this paper, with the combinative addition of La and B elements, the grain refinement of Al–Si alloys with different contents of Si was achieved. Compared to individual addition of B element, the combinative addition of La and B elements can effectively refine the grains of Al–Si alloys. The addition of La element suppresses the mutual poisoning between Sr and B elements, benefiting the formation of a fully modified eutectic silicon structure in the Al–Si alloys. This work also indicates that the tensile properties, especially the elongation, of Al–Si alloys are enhanced with the addition of La element.