Effects of heat-treatment temperature on properties of co-continuous β-Si₃N₄ reinforced al matrix composites

The co-continuous β-Si₃N₄ reinforced Al matrix composites were fabricated through squeeze casting of porous β-Si₃N₄ preforms with porosity of 53.43% which obtained by pressureless sintering. The influences of heat-treatment temperature on the microstructures and mechanical properties of co-continuous β-Si₃N₄ reinforced Al matrix composites were investigated. With the heat-treatment temperature increase, the degree of interfacial reaction, dislocation density increase, and vickers hardness increases, while fracture toughness decreases, accompanied by flexural strength increasing until 850℃ and then decreasing. The fracture mode of composites changes gradually from ductile intergranular rupture to brittle intergranular rupture. When being heat-treated at 850℃, the composites obtain the optimum mechanical properties with the reaction layer of about 20-50 nm.