稀土对MoSi2力学性能和抗氧化性能的影响

采用自蔓延和真空烧结方法制备了掺杂0．9％La2O3的MoSi2基复合材料，利用热重分析法，SEM和X射线考察了La2O3颗粒对MoSi2力学性能、抗氧化特性以及循环氧化后力学性能的影响。结果表明，与纯MoSi2相比，RE／MoSi2材料的弯曲强度和断裂韧性分别提高了46％和78％；稀土对MoSi2材料的强韧化机制主要是细晶强化、弥散强化和细晶韧化。RE／MoSi2的氧化增重是纯MoSi2的2．5倍，稀土使MoSiz材料的抗氧化性能降低。由于纯MoSi2材料氧化后的晶粒长大，其抗弯强度比氧化前降低了17％。稀土对MoSi2氧化时的晶粒长大倾向有抑制作用，使得RE／MoSi2材料的抗弯强度基本不变。

Effect of Rare Earths on Mechanical Properties and Oxidation Resistance of MoSi2

The MoSi2-based composites doped with 0.9% La2O3 were synthesized by serf-propagating high temperature synthesis and vacuum sintering. The effect of La2O3 particle on the mechanical properties, oxidation behavior and mechanical properties as-oxi- dized were investigated by TGA, SEM and X-ray. Results showed that flexure strength and fracture toughness were improved by 46% and 78% respectively compared with pure MoSi2. The strengthening and toughening mechanism of RE/MoSi2 were fine-grain toughening, dispersion strengthening and fine grain toughening. The weight change of RE/MoSi2 was almost 2.5 times as much as pure MoSi2. The oxidation resistance of RE/MoSi2 weakened. Because the grain of pure MoSi2 as-oxidized became coarser, the flexure strength decreased by 17% compared with MoSi2 assintered. The rare earths could inhibit the grain growth of MoSi2 during oxidation process and the flexure strength of RE/MoSi2 composites almost remained unchanged.