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采用添加剂热压烧结制备了短纤维增韧氮化硅基复合材料,并对材料的力学性能和微观结构进行了分析和讨论。结果表明:Y2O3-La2O3添加剂促进了α-Si3N4→β-Si3N4的相转变,这个体系经过1800℃的热压烧结后,其中的碳纤维产生退化。而经过1600℃热压烧结的含LiF-MgO-SiO2添加剂的体系中,纤维保持完好,晶粒没有发生相转变。两个体系的复合材料的断裂韧性值均高于氮化硅基体的值,其提高幅度均接近20%,这归因于纤维拉拔、裂纹偏转和界面松解机制。
The short fiber toughened silicon nitride matrix composites were prepared by hot press sintering with additives. The mechanical properties and microstructure of the composites were analyzed and discussed. The results show that the Y2O3-La2O3 additive promotes the phase transformation of α-Si3N4 → β-Si3N4. After this system is sintered at 1800 ℃, the carbon fiber is degraded. In the system containing LiF-MgO-SiO2 additive sintered at 1600 ℃, the fibers remained intact and the grains did not undergo phase transformation. The fracture toughness of the composites of the two systems are higher than that of the silicon nitride matrix, and the increasing range is nearly 20%, which is attributed to the fiber drawing, crack deflection and interfacial release mechanism.