Study on the Mechanical Properties of Soluble Magnesium-Based Composites Reinforced with Graphite Particles and Carbon Fiber

In this study, graphite particles and short-cut carbon fibers were used to prepare a hybrid-reinforced composite with AZ91 magnesium alloy as the matrix via the powder metallurgy process. The effects of different added phase ratios on microstructure, density, compressive strength, and fracture morphology were investigated. The results show that the addition of 5% graphite particles alone reduced the compressive strength by 20.1% compared to pure magnesium, attributed to interfacial delamination and interlaminar peeling in the graphite’s layered structure. The introduction of carbon fibers effectively compensates for this degradation. When the carbon fiber content was increased to 10% (with graphite fixed at 5%), the compressive strength reached a peak of 375 MPa—a 63.0% increase over the graphite-only system—and the fracture strain rose to 16.98%. However, an excessive amount of carbon fibers (15%) led to agglomeration, causing the porosity to rise to 9.1% and resulting in a significant decline in mechanical properties. Microstructural analysis indicates that carbon fibers exert a reinforcing effect by sharing the load and constraining the lateral deformation of the matrix, while graphite particles induce microcracks and pores, resulting in a weakening effect; under appropriate ratios, the two can achieve synergistic reinforcement. This study provides experimental evidence for the component design and performance control of high-strength, rapidly dissolving magnesium-based composites.