Effect of Al2O3 Particle Size on Mechanical Properties of Ultrasonic-Assisted Stir-Casted Al A356 Matrix Composites

In this study, aluminum A356 (AlSi7Mg0.3) alloy matrix composites reinforced with various fractions (0.5, 1.0 and 1.5 wt%) of Al ₂O ₃ particles having two different particle sizes (nano- and micro-size) were produced, and the effect on mechanical properties of aluminum metal matrix composite was examined. Ultrasonic-assisted mechanical stirring process (hybrid stirring) was used in order to improve the distribution of reinforcements in the matrix. T6 heat treatment process was applied afterward. Microstructures were characterized by metallographic analysis, grain size measurement and DAS measurements. Mechanical properties were evaluated with uniaxial tensile tests, charpy tests and hardness tests. The highest values of ultimate tensile strength (UTS) and elongation were obtained with 0.5 wt% of nano-Al ₂O ₃ addition among all compositions. Compared to the reference sample, UTS values are increased 8.7% and 3.9% with 0.5 wt. of nano-Al ₂O ₃ and 1.5 wt% of micro-Al ₂O ₃ addition, respectively. Moreover, the Charpy impact energy was increased with a maximum of 41% with 0.5% nano-Al ₂O ₃ addition. As a result, 0.5 wt% of nano-Al ₂O ₃ addition yields the optimum properties according to the quality index calculations.