Grain refinement in ultrasonicated binary aluminium alloys

•Conventional technique for estimating the growth restriction factor is less accurate for near-eutectic alloys.•Scheil-Gulliver solidification simulation enabled accurate estimation of growth restriction factor.•Supercooling parameter better explains the grain refinement in near-eutectic Al-Ni alloys. Combined effect of solute concentration and ultrasonic treatment on the grain refinement of aluminium based alloys is studied. Silicon, copper, and nickel solutes are used. Upon ultrasonic treatment, grain refinement in Al-3 wt.%Ni alloy is more pronounced than that in Al-3 wt.%Si alloy, although the growth restriction factor of solute silicon is twice that of nickel in pure aluminium. These observations spurred this investigation about the grain refinement mechanisms operating in Al-based hypoeutectic alloys. Grain refining efficiency of different solutes is analyzed using the growth restriction factor and constitutional supercooling parameter, both calculated from Scheil-Gulliver solidification simulation. It is observed that grain refinement occurring from ultrasonic treatment in near-eutectic alloys is better explained by using the constitutional supercooling parameter rather than the growth restriction factor.