Processing, microstructure and tensile properties of nano-sized Al2O3 particle reinforced aluminum matrix composites

Nano-sized ceramic particle reinforced aluminum matrix composites fabricated using conventional stir casting technique usually present poor distribution of nanoparticles within the matrix and high porosity. In this study, nano-Al2O3/2024 composites were prepared by solid–liquid mixed casting combined with ultrasonic treatment. The obtained composite exhibited fine grain microstructure, reasonable Al2O3 nanoparticles distribution in the matrix, and low porosity. Solid–liquid mixed casting technique was effective in inhibiting the agglomeration of nanoparticles in the matrix. The application of ultrasonic vibration on the composite melt during the solidification not only refined the grain microstructure of the matrix, but also improved the distribution of nano-sized reinforcement. Compared with the matrix, the ultimate tensile strength and yield strength of 1 wt.% nano-Al2O3/2024 composite were enhanced by 37% and 81%, respectively. The better tensile properties were attributed to the uniform distribution of reinforcement and grain refinement of aluminum matrix.