Microstructure and Mechanical Properties of Al/MgAl2O4 In Situ Composites Synthesized by Ultrasonic Cavitation

Al–4Mg/MgAl 2 O 4 composites were successfully synthesized by the in situ reaction of Al–4Mg alloy melt and H 3 BO 3 precursor in the presence of ultrasonic cavitation field. Ultrasonic-assisted synthesis facilitated generation of ~ 350-nm-sized MgAl 2 O 4 particles. Enhanced reaction along with dispersion of MgAl 2 O 4 was perceived due to the synergetic effect of ultrasonic cavitation. The presence of MgAl 2 O 4 particles resulted in 3–4 times reduction in matrix alloy grain size, and the grain refinement was further enhanced by ultrasonic treatment. Compared to unreinforced alloy, ultrasonicated Al/MgAl 2 O 4 composite exhibited an improvement in ultimate tensile strength by ~ 30 MPa with ~ 85% of ductility retention. Grain boundary strengthening, Orowan dispersion strengthening, coefficient of thermal expansion mismatch strengthening and load-bearing strengthening were the anticipated mechanism for enhancement in mechanical properties.