Microstructure and mechanical properties of high-pressure-assisted solidification of in situ Al–Mg2Si composites

In this study, an Al–Mg2Si composite was solidified under a high pressure of 3 GPa and the effects on microstructural evolution, mechanical properties including hardness, friction, and wear behavior, and compression properties were investigated. The results indicate that the composite solidified under high pressure exhibited significantly enhanced hardness, compressive properties, wear, and friction resistance compared to the as-cast and solid solution–treated (ST) composites. The hardness of the composites under high-pressure solidification was 2.25 times and 1.37 times those of the as-cast and ST composites, respectively. The compressive yield strength, elastic modulus, and compressive strain were 121.5 MPa, 29.6 GPa, and 22.3% for the as-cast composite, 146.1 MPa, 44.5 GPa, and 35.8% for the ST composite, and 151.3 MPa, 49.3 GPa, and > 75% for the high-pressure-solidified composite, respectively. The friction coefficient of the composite under high-pressure solidification was only 44% of that of the as-cast composite and 67% of that of the ST composite. The wear modes were adhesive wear and abrasive wear for the as-cast composite, but only abrasive wear for the composite solidified under high pressure; the fracture mode transformed from cleavage fractures in the as-cast composite to quasi-cleavage fractures in the composite solidified under high pressure.