Si_3N_4颗粒和纳米SiC晶须强韧化MoSi_2基复合材料

MoSi_2-based Composites Reinforced and Toughened by Si_3N_(4(p)) and Nano SiC_(w)

用真空热压法制备了Si3N4颗粒和纳米SiC晶须强韧化MoSi2基复合材料。采用X射线衍射仪、金相显微镜、扫描电镜分析了该材料的物相、微观组织结构和断口形貌,测算了其致密度、晶粒尺寸、抗弯强度和断裂韧性。结果表明:复合材料致密性好;添加的Si3N4和SiC与基体有着很好的化学相容性;与纯MoSi2相比,复合材料晶粒明显细化,抗弯强度和断裂韧性明显增加。其中MoSi2+20%Si3N4+10%SiC抗弯强度达400MPa,比纯MoSi2提高了58.7%;断裂韧性达6.1MPa.m1/2,比纯MoSi2提高了108.9%。复合材料的强化机制为细晶强化和弥散强化;韧化机制为细晶韧化、裂纹偏转和裂纹微桥接。

MoSi2-based composites reinforced and toughened by Sia N4 particle and nano SiC whisker were prepared by vacuum hot-pressing. The phase component, microstructure and fracture morphology of composites were analyzed by means of X-ray diffractometer, scanning electron microscope and metallographic microscope. The relative density, grain size, bending strength and fracture toughness of composites were measured. The results show that the composites have high density. There is no chemical reaction among Sis N4, SiC and MoSi2 during the hot-pressing process. The bending strength and fracture toughness of the MoSi2 ＋ 20 % Sia N4 ＋ 10 % SiC composite are 400MPa and 6.1 MPa · m^1/2 respectively, which are 58.7% and 108.9% higher than that of pure MoSi2, respectively. The strengthening mechanisms of composites are fine grain strengthening and dispersion strengthening. The toughening mechanisms are fine grain toughening, crack deflection and microcrack bridging.