超细晶硬质合金显微组织参数与力学性能定量关系的研究

QUANTITATIVE RELATIONSHIPS BETWEEN MICROSTRUCTURE PARAMETERS AND MECHANICAL PROPERTIES OF ULTRAFINE CEMENTED CARBIDES

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d_(WC),Co相平均自由程L_(Co)和WC晶粒邻接度C_(WC-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C_(WC-WC)基本相同时,超细晶硬质合金的硬度分别与d_(WC)^(-1/2)和L_(Co)^(-1/2)成线性正比关系,断裂韧性K_(IC)分别与d_(WC)^(-1/2)和L_(Co)^(-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C_(WC-WC)的增大,超细晶硬质合金的横向断裂强度降低,且当C_(WC-WC)>0.5时,硬质合金的强度随C_(WC-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.