Hybrid reinforced AZ91 Mg alloy composites with Al 2O 3 short fibers and graphite particles containing different content and granularity were successfully prepared in squeezing casting.The processes
microstructure and properties of the composites were investigated.It was found that enhancement phase is not only uniformly distributed in the composites but also closely bonded with the matrix
in which the obvious casting defects can not be found.The hardness of the composites was decreases with the increase of the graphite content and with the refinement of the graphite particle size.