对超细晶WC-Co硬质合金的复相显微组织进行了系统的定量化表征和分析, 获得了WC晶粒尺寸dWC, Co相平均自由程LCo和WC晶粒邻接度CWC-WC等显微组织参数与力学性能的定量关系, 模型预测结果与实验测定结果符合很好. 结果表明, 当CWC-WC基本相同时, 超细晶硬质合金的硬度分别与dWC-1/2和LCo-1/2成线性正比关系, 断裂韧性KIC分别与dWC-1/2和LCo-1/2成确定性函数关系. 在Co含量一定、WC平均晶粒尺寸基本相同的情况下, 随着 CWC-WC的增大, 超细晶硬质合金的横向断裂强度降低, 且当CWC-WC>0.5时, 硬质合金的强度随CWC-WC增加显著下降.
The microstructures of ultrafine WC-Co cemented carbides were characterized and analyzed by stereological methods. The quantitative relationships between the mechanical properties and microstructure parameters, such as the mean grain size dWC, mean free path LCo and contiguity CWC-WC, were obtained. The calculated results of mechanical properties agree well with the experimental measurements. With the equivalent contiguity, the Vickers hardness of ultrafine cemented carbides has linear relationships with dWC-1/2 and LCo-1/2 and the fracture toughness KIC has deterministic relationships with dWC-1/2 and LCo-1/2, respectively. With certain Co content and mean grain size, the transverse rupture strength decreases with the increase of contiguity. Especially when the contiguity is above 0.5, the strength decreases obviously. The present results may be used as criteria to optimize the microstructure and to improve mechanical properties of ultrafine cemented carbides.
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