Abstract
In this work, AA 2024 wrought aluminium alloy was reinforced with Al2O3 nanoparticles to fabricate surface metal matrix nanocomposites (MMNCs) via friction stir processing (FSP). Processing parameters, namely, rotational speed, traverse speed and the number of processing passes, were investigated to study their effects on the wear resistance, mechanical properties and hardness behaviour of the MMNCs. The mechanical properties of the materials were evaluated in a tensile test, and their hardness and wear properties were determined through Vickers microhardness and weight loss tests, respectively. Microstructural observation revealed that the processing parameters influenced the mechanical properties, wear behaviour, and hardness properties of the MMNCs. Specifically, the FSP refined the microstructural grains to a level 19 times better than that achieved with base alloy, thereby fine-tuning the average base alloy grain size of 135 μm to an average of 7 μm. Increasing the number of passes improved wear resistance by an average of 39%–70%, and implementing a third round of FSP enhanced the ultimate tensile strength and Young’s modulus by 40% and 20% on average, respectively. Finally, the incorporation of Al2O3 nanoparticles increased the hardness of the MMNCs by an average of 42%.