Fabrication and mechanical properties of squeeze cast Mg matrix composites

In the present study, AZ91 Mg matrix composites were fabricated with a variation of the applied pressure using squeeze infiltration technique. Alumino-silicate short fibers, alumina short fibers and aluminium-berate whiskers were used as reinforcements. Preforms of reinforcements from the slurries were consolidated by vacuum suction method, and then calcinated. The effects of squeeze casting conditions including applied pressure and the preheating temperatures of the mold and preforms, etc on the solidification microstructure of the Mg matrix composites were investigated. Bending strength and fracture toughness were measured to evaluate mechanical properties of the squeeze cast Mg matrix composites. In-situ SEM fracture test was performed to observe the microfracture process of the Mg matrix composites. Correlation between microstructure and microfracture process was studied. Proper choice of preform fabrication conditions such as the modification of slurry composition and calcination temperature improved the microstructure and properties of the squeeze cast Mg matrix composites. The fracture behavior of the composites has somewhat different features with different applied pressure and reinforcements. It was found that the optimal applied pressure exists for the fabrication of the Mg matrix composites for different reinforcements.