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用分析电镜和带有拉伸台的高压电镜,研究了YG8R、YT5R和YT14R稀土硬质合金的微观组织和裂纹扩展特征。结果表明,添加铈在硬质合金中可能形成Ce_2O_3或Ce_2O_2S化合物,它抑制了层错扩展和fcc Co向hcp Co的转变,增加了合金中fcc Co的体积分数,提高了Co相和(TiW)C相及晶界的强度和韧性。拉伸裂纹边沿的Co相有明显的塑性变形特征,且裂纹可以穿过一些较小的WC颗粒。
The microstructures and crack propagation characteristics of YG8R, YT5R and YT14R rare earth cemented carbide were studied by means of SEM and high-voltage electron microscope with a tension stage. The results show that Ce_2O_3 or Ce_2O_2S compounds may be formed in cemented carbide by adding cerium, which inhibits the growth of stacking faults and the transformation of fcc Co to hcp Co, increases the volume fraction of fcc Co in the alloy and increases the Co phase and (TiW) C phase and grain boundary strength and toughness. The Co phase at the edge of the tensile crack has obvious plastic deformation characteristics, and the crack can pass through some smaller WC particles.