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在非均相沉淀法制备的Fe-Mo包覆Si_3N_4陶瓷粉末中添加助剂MgO-Y_2O_3进行常压烧结,采用X线衍射仪(XRD)、电镜扫描(SEM)等方法研究了不同温度下Mo元素对该Si_3N_4陶瓷相组成、显微结构和力学性能等方面的影响。结果表明:Mo元素与Fe及Si_3N_4反应生成Fe_3Mo_3N化合物,温度升高其分解为金属Fe相与MoSi_2,同时组织中出现大量液相促使晶型发生转变并实现液相烧结。该材料在1 650℃时维氏硬度(1507)为最高,在1700℃时密度(3.821 3 g/m~3)抗弯强度(908.2 MPa)、断裂韧性(12.08 MPa·m~(1/2))为最高,当烧结温度为1 750℃时,金属Fe相仍得以保留,生成了极大颗粒MoSi_2,材料微观结构恶化,密度、性能迅速下降,所以最佳烧结温度控制在1 700℃左右。
The additives MgO-Y_2O_3 were added into the Fe-Mo coated Si_3N_4 ceramic powders prepared by the heterogeneous precipitation method under atmospheric pressure. XRD, SEM and other methods were used to study the effects of Mo Element on the Si_3N_4 ceramic phase composition, microstructure and mechanical properties and other aspects. The results show that the Mo element reacts with Fe and Si_3N_4 to form Fe_3Mo_3N compound. When the temperature rises, it decomposes into metallic Fe phase and MoSi_2. At the same time, a large amount of liquid phase appears in the microstructure to change the crystal phase and achieve liquid phase sintering. The material has the highest Vickers hardness (1507) at 1 650 ℃, the flexural strength (908.2 MPa) and the fracture toughness (12.08 MPa · m ~ (1/2) at 1700 ℃) )) Is the highest. When the sintering temperature is 1 750 ℃, the metallic Fe phase is still retained, and the extremely large particles of MoSi2 are formed. The microstructure of the material is deteriorated and the density and performance decrease rapidly. Therefore, the optimal sintering temperature is controlled at about 1700 ℃ .