Investigation of Microstructural and Mechanical Properties of Mg-HEA Nanocomposite Through Ultrasonic Assisted Two Step Stir Casting Technique

In this study, nano-sized 1 wt. % high entropy alloy (HEA) particles (Al4CrFeMnTi0.25) are used as a novel kind of reinforcement in a magnesium (AZ91D) matrix. A high-strength nanocomposite has been developed using the novel technique of ultrasonic-assisted two-step stir casting, and efforts have been made to minimize reinforcement agglomerations and maximize a uniform and smooth interface for efficient load transfer. Ultrasonic-assisted two-step stir casting is used in an inert atmosphere to thoroughly wet high entropy alloy particles (HEAp) in a molten magnesium (AZ91D) alloy to produce nanocomposites. Due to the potential of HEA particles to act as grain boundary pinning and nucleation sites, recrystallized small grains were observed in nanocomposites. The microstructure of the nanocomposite was analyzed using an optical microscope, and the results showed that HEAp was evenly dispersed throughout and well bonded to the matrix. The hardness of nanocomposites containing HEAp as a reinforcement is significantly enhanced due to the fine grains and the intrinsically high hardness of HEA particles. The mechanical behaviour of the nanocomposite was evaluated and compared with that of the unreinforced magnesium (AZ91D) alloy.