Grain refinement of hypoeutectic Al-7wt.%Si alloy induced by an Al–V–B master alloy

The current study investigates the grain refinement of an Al-7wt%Si alloy with addition of Al–V–B master alloy. It is found that the Al–V–B master alloys can overcome the Si poison effect on grain refinement and refine the as cast grain structure of the Al-7wt%Si alloy effectively. A remarkable grain refinement has been achieved by using an Al–3V–1B master alloy with the combined inoculation of 0.015 wt% V and 0.005 wt% B, compared to that obtained by separate inoculation of Al–5V and Al–3B master alloys with the same concentrations of V and B. The corresponding XRD analysis on the Al–5V and Al–3V–1B master alloys and extracted particles from the Al–3V–1B master alloy show that the active nuclei are VB2 particles. The employment of the new Al–3V-1.28B master alloy optimized according to the atomic ratio of V:B = 1:2 produced the finest grain size in the Al-7wt.%Si alloy compared with the commercial Al–3Ti–1B and Al–5Ti–1B master alloys. This study indicates that the Al–V–B master alloy has the potential to be an effective grain refiner for Al–Si alloys. •A new potential grain refiner for Al–Si alloys, Al–V–B refiner, is employed to induce the grain refinement.•The optimized Al–V–B refiner can produce the finest grain size in the Al-7wt.%Si alloy compared with the Al–Ti–B refiners.•VB2 particles supplied by Al–V–B master alloy are the active nuclei for heterogeneous nucleation in Al-7wt.%Si alloy.