Ultrasonic assisted grain refinement of Al–Mg alloy using in-situ MgAl2O4 particles

•Ultrasonic treatment aids in-situ MgAl2O4 particle formation.•MgAl2O4 particles act as a heterogeneous nucleation sites.•Nucleation on MgAl2O4 is enhanced by ultrasonic treatment.•7–8 Fold reduction in grain size is observed after ultrasonic treatment.

MgAl2O4 particles were in-situ synthesised in Al–Mg melts using SiO2 precursor assisted by ultrasonic treatment (UT). 7 to 8 Fold reduction in grain size is achieved in Al–1Mg–0.1SiO2 alloy subjected to 5 min UT. Reason behind the grain reduction is explained in terms of ultrasonic cavitation activated SiO2 reduction reaction, thereby increasing the number density of MgAl2O4 particles and their wettability.