The hard WC-Co composites usually have weak toughness. The present work solved this issue by a new strategy of fabricating nanocrystalline composites, which consists of concurrent crystallization, carbonization, and sintering densification of the amorphous compound powder. The resultant nanocrystalline WC-Co composite has distinctly larger proportion of interfacial coherency at the grain- and phase-boundaries compared with that in the conventional counterparts. The formation mechanisms of the coherent WC grain boundaries, Co twinning boundaries, and step-like semi-coherent WC/Co phase boundaries were demonstrated on the atomic scale. Moreover, the contributions of the characteristic interfaces to the resistance against intergranular fracture, which dominates the failure of nanocrystalline composites in the deformation, were illustrated based on the analyses of atomic configuration and crystallographic relationship at interfaces. The reasons were disclosed for the advanced comprehensive properties with simultaneously ultrahigh hardness and fracture toughness of the prepared nanocrystalline composite. The present technology and mechanisms for properties enhancement will be applicable to a large variety of composite materials.

硬质WC-Co复合材料通常具有较弱的韧性。本工作通过一种制备纳米晶体复合材料的新策略解决了这一问题，该策略包括同时结晶，碳化和无定形化合物粉末的烧结致密化。与常规对应物相比，所得纳米晶WC-Co复合物在晶界和相界处具有明显更大的界面相干性比例。在原子尺度上证明了相干的WC晶粒界，Co孪晶界和阶梯状半相干的WC / Co相界的形成机理。此外，特征界面对抗晶间断裂的贡献，主要是纳米晶复合材料在变形中的破坏，在分析界面原子结构和晶体学关系的基础上进行了说明。公开了制备的纳米晶复合材料具有先进的综合性能同时具有超高硬度和断裂韧性的原因。用于增强性能的本技术和机制将适用于多种复合材料。