中文摘要：

以粒度为5μm的粗WC颗粒和粒度为1μm的细WC颗粒为原料,采用6种不同的粗/细颗粒质量配比,通过低压烧结制备Co含量（质量分数,下同）为7%的低钴WC–Co硬质合金,测试材料的抗弯强度、断裂韧性和硬度,并采用扫描电镜（SEM）观察材料的微观组织、弯曲断口形貌及裂纹扩展情况,研究粗颗粒WC含量对低钴硬质合金组织与性能的影响。结果表明,随粗颗粒WC含量增加,WC晶粒度的分布表现为明显的双峰结构特征,从合金的弯曲断口观察到裂纹偏转以及穿晶断裂数量显著增加,以此阻碍裂纹扩展,从而提高合金的韧性。合金硬度随粗颗粒WC含量增加而下降。当粗颗粒含量（质量分数）为50%时,WC-7%Co硬质合金具有较好的综合力学性能,其硬度（HV30）为15.9 GPa,抗弯强度和断裂韧性分别为2 490 MPa和11.39 MPa·m^1/2。

英文摘要：

Using WC with different particle sizes （5 μm and 1 μm） as raw material, six kinds of WC-7% Co （mass fraction, the same below） cemented carbides with different coarse/fine particle mass ratios were produced through low-pressure sintering. The effects of coarse grained WC additions on microstructure and properties of low-Co content WC-Co cemented carbides were investigated by testing transverse rupture strength （TRS）, fracture toughness （Kic） and hardness （HV3o）. The microstructure, fracture morphology and crack propagation were observed through scanning electron microscopy （SEM）. The results show that the distribution of WC grains exhibits bimodal structure with increasing the addition of coarse-grained WC powder. At the same time, the obvious crack deflection and transgranular fracture phenomenon can be observed, which can resist the crack propagation and imporve the toughness of cemented carbides. The hardness of alloys decreases with increasing the content of coarse grained WC. When the percentage of addition is 50%, the optimal mechanical properties of WC-7% Co alloy are obtained with the hardness, transverse rupture strength and fracture toughness values being 15.9 GPa, 2 490 MPa and 11.39 MPa-m^1/2, respectively.