Abstract:The magnesium matrix composites reinforced by graphite particles and Al₂O₃ short fibers were fabricated by squeeze-infiltration technique. The additions dispersed uniformly and no agglomeration and casting defect were observed. The microstructures and wear properties of the composites with different Ce contents of 0, 0.4%, 0.8% and 1.0%, respectively, were investigated. Especially, the effect of Ce on the properties was discussed. The results reveal that Ce enriches around the boundaries of graphite particles and forms Al₃Ce phase with Al. The addition of Ce refines the microstructures of the composites. With the increase of Ce content, the grain size becomes smaller and the wear resistance of the composite is improved. At low load, the composites have similar worn surface. At high load, the composite with 1.0% Ce has the best wear resistance due to the existence of Al₃Ce phase. The Al₃Ce phase improves the thermal stability of the matrix so the graphite particles can keep intact, which can still work as lubricant. At low load, the wear mechanism is abrasive wear and oxidation wear. At high load, the wear mechanism changes to delamination wear for all the composites.

Key words: magnesium matrix composite; graphite; Ce; wear property