α-SiAlON/SiCnp复合材料在室温和高温下的显微结构与力学性能

Microstructure and Mechanical Properties of α SiAlON/nano sized SiC at Ambient and Elevated Temperature

本文采用机械混合Ｓｉ３Ｎ４，ＡｌＮ，Ａｌ２Ｏ３，Ｄｙ２Ｏ３和纳米β－ＳｉＣ粉料，通过热压烧结，制备了１０ｗｔ％纳米ＳｉＣ颗粒增强α－ＳｉＡｌＯＮ复合材料。力学性能测试表明，在室温时复合材料的维氏硬度，压痕断裂韧性和三点弯曲强度比单相α－ＳｉＡｌＯＮ略高。但复合材料的三点弯曲强度可以保持到１０００℃，其值为这时单相α－ＳｉＡｌＯＮ的两倍。断口形貌表明复合材料的晶粒尺寸比单相α－ＳｉＡｌＯＮ的小，这两种材料的室温断裂方式均以穿晶断裂为主。研究表明，低粘度的玻璃相是造成单相α－ＳｉＡｌＯＮ高温性能下降的主要原因，而纳米ＳｉＣ的加入可以促使晶界相结晶，从而使复合材料的高温性能维持到较高的温度。

Nano sized β Sic mixed with Si 3N 4, AlN, Al 2O 3, Dy 2O 3 was hot press sintered to form the composite of α SiAlON/10wt% nano sized SiC. The hardness, toughness and three point bending strength of the composite at ambient temperature are a little higher than those of α SiAlON, while the bending strength was maintained up to 1000℃ and about 2 times of that of α SiAlON at 1000℃. According to the fracture surfaces, the grain size of the composite was smaller than that of α SiAlON and both of them have predominately transgranular mode of fracture. It was believed that the decrease of the bending strength of α SiAlON at elevated temperature was caused by the viscous flow of the grain boundary phase, while the addition of nano sized SiC particles effectively increased viscosity of grain boundary phase by promoting it crystalized and therefore prevented the strength loss of α SiAlON/nano sized SiC composites at elevated temperature.