AA2024/SiC metal matrix composites simultaneously improve ductility and cracking resistance during elevated temperature deformation

Abstract This study uses the stir-casting technique to combine a semi-solid AA2024 alloy directly with finely-sized β-SiCp embedded as a powder or with mechanically alloyed granules as a delivery agent. Liquid-state primary fabrication tends to form agglomerates of reinforcement particles, whereas rolling better distributes the composite constituents. Sub-micron reinforcements of low volume fractions do not significantly increase the hardness of the composite materials. Uniaxial tensile testing at elevated temperatures over a wide range of strain rates showed simultaneous increases in the ductility and crack resistance of AA2024 + SiCp granules embedded as a powder when compared to the non-reinforced control material at lower strain rates, with the same toughness as the control material. The maximum engineering strain of 252.7 ± 19.2% was observed in AA2024/SiCp at a strain rate of 10−4 s−1. This improvement in properties is attributed to grain refinement in the MMCs, leading to pinning events during the straining and ductility increases. The resultant impediments to grain growth and crack propagation allow the fine-sized reinforcements to control dynamic microstructural changes during fatigue. Cube {001} is a dominant texture component in AA2024, whereas the Goss {011} and S {123} components mainly represent the texture of the discontinuously reinforced aluminum matrix.