Effects of reheating time on microstructure and tensile properties of SiCp/2024 Al-based composites fabricated using powder thixoforming

The present investigation addresses a new technology, named powder thixoforming, used to fabricate SiCp/2024 Al-based composites. The effects of reheating time on microstructure and mechanical properties have been studied. The results indicated that the quantity of liquid, the coarsening behavior of the primary particles, the subsequent plastic deformation occurring during thixoforging, and thus the resulting microstructural compactness and mechanical properties changed as a function of reheating time. The best comprehensive tensile properties of the composite, that is an ultimate tensile strength of 370 MPa and an elongation of 4.4%, were obtained after reheating for 80 min at 625 °C, which was an increase of 23.3% and a decrease of 57.7%, respectively, compared to the 2024 alloy thixoforged under the same conditions as the composite. The fracturing in the composites occurred through interconnecting cracked SiCp and debonded SiC/Al interfaces caused by a higher concentration of stress and a coalescence of microvoids.