Effects of particle size and properties on the microstructures, mechanical properties, and fracture mechanisms of 7075Al hybrid composites prepared by squeeze casting

To investigate the effects of particle size and properties on the mechanical properties of 7075Al matrix composites, hybrid composites reinforced using three different reinforcement combinations, 40 vol. % 7 μm SiCp with 5 vol. % 7 μm SiCp, 35 μm SiCp, and 35 μm Ti, were prepared using squeeze casting. The failure mechanisms and the microstructure–property relationships of hybrid composites were studied using SEM, TEM, and tensile tests. The composite containing Ti particles achieved the highest tensile strength of 626 MPa and an elongation of 1.2 %. Fracture mechanism analyses imply that the reduced strength for the 35 μm SiCp-containing composite are caused by the inefficient load transfer capability resulting from the preferential breakage of larger-sized SiCp particles during the deformation process. In contrast, micro-zones formed by Ti particles at the center and matrix alloy with few dislocations around release stress and deform synergistically during deformation, which decreases the breakage of SiCp and improves the plastic deformation ability of the matrix alloy, resulting in a good combination of strength and ductility.