Effects of Ultrasonic Treatment on Microstructure and Properties of Al-Based Composites Reinforced by In Situ Al2O3 Nanoparticles

Abstract

AbstractAn investigation on the microstructure of as-cast Al-Mg-Cu composites reinforced by in situ nano-sized Al2O3 dispersoids with ultrasonic treatment showed that ultrasonic treatment of the melt prior to casting had a significant effect on the size and sphericity of α-Al dendrites as well as on the size, continuity and sphericity of intermetallic particles (Al2CuMg) formed during cooling and solidification of the composite. More importantly, Al2O3 nanoparticles were uniformly distributed inside the grains, which were in situ produced by the displacement reaction between Al and CuO in the melt under ultrasonic treatment. The microstructural effects were mainly attributed to the cavitation and streaming phenomena which took place during ultrasonic treatment in the melt. The mechanical properties were investigated by tensile tests and hardness measurements. Ultrasonic treatment caused a significant increase in the yield strength (~43%), ultimate tensile strength (~32%) and hardness (~13%), and simultaneously slight improvement in the ductility.