力学性能和高温氧化行为
(1. 中南大学 粉末冶金国家重点实验室， 长沙 410083；
2. 湖南科技大学 材料表面工程研究所， 湘潭 411201)
摘 要: 通过自蔓延高温合成了稀土协同Mo5Si3复合强韧化MoSi2的复合粉末， 研究了La2O3-Mo5Si3/MoSi2复合材料的室温力学性能和高温氧化特性。结果表明： 与纯MoSi2相比， 稀土和Mo5Si3细化了材料的晶粒，提高材料的室温弯曲强度和断裂韧性， 其强化机制为细晶强化， 韧化机制为细晶韧化、 裂纹偏转、 裂纹分支和微桥接； 当Mo5Si3含量不超过30%（摩尔分数）时， 随着Mo5Si3含量的增加，材料的抗氧化性能降低， 而RE-40%Mo5Si3/MoSi2（摩尔分数）复合材料出现粉化现象； RE-Mo5Si3/MoSi2复合材料抗氧化性的降低，主要是由于Mo5Si3较差的抗氧化性、 材料致密度的降低以及晶粒细化的结果； 0.8%稀土（质量分数）协同5% Mo5Si3（摩尔分数）的RE-Mo5Si3/MoSi2复合材料具有较好的综合力学性能和高温抗氧化特性。
关键字: Mo5Si3； MoSi2； 稀土； 力学性能； 氧化行为
（1. State Key Laboratory of Powder Metallurgy,
Central South University, Changsha 410083, China;
2. Institute of Material Surface Engineering,
Hunan University of Science and Technology, Xiangtan 411201, China）
Abstract: The MoSi2-based composites containing La2O3 earth and different volume fractions of Mo5Si3 were synthesized by self-propagating high temperature synthesis. The mechanical properties of MoSi2 matrix composites and high temperature oxidation behavior were studied. The results show that additions of La2O3 earth and Mo5Si3 refine the grain size of the MoSi2 matrix composite and improve the flexure strength and fracture toughness at room temperature in contrast with pure MoSi2. The strengthening mechanism of La2O3-Mo5Si3/MoSi2 is fine-grain strengthening, and the toughening mechanisms are fine-grain toughening, crack deflection, crack branching and crack microbridging. When the Mo5Si3 content does not exceed 30%(mole fraction), the oxidation resistance of La2O3-Mo5Si3/MoSi2 decreases with the increase of Mo5Si3 content. However, the RE-40%Mo5Si3/MoSi2(mole fraction) composite occurs pesting because of the poor oxidation resistance of Mo5Si3, decrease of relative density and grain refinement of the composites. The La2O3-Mo5Si3/MoSi2 composite has optimal mechanical properties and high temperature oxidation resistance with additions of 0.8%La2O3(mass fraction) and 5% Mo5Si3(mole fraction).
Key words: Mo5Si3；MoSi2; rare earth; mechanical properties; oxidation behavior
