Considerable efforts have been made to manufacture composite materials with low density and to enhance the specific strength of metals and alloys by adding boron carbide particles. One of the major factors in enhancing the mechanical properties of these composites is the interfacial characteristics of the metal/ceramic interface, particularly the strength of the bonding between the metal/ceramic interface. Here we investigate the microstructure and interfacial characteristics of the boron carbide-nickel (B4C-Ni) and silicon carbide-boron carbide (SiC-B4C) composites processed in the solid state at relatively high pressure, using transmission electron microscopy. The sintered boron carbide and nickel powders showed improved hardness and modulus, which is attributed to the formation of nickel boride (Ni4B3) at the nickel-boron carbide interface. Using fine-probe energy dispersive spectroscopy and high-angle annular dark field imaging, we observed a Si-rich intermixing layer for the silicon carbide-boron carbide interface, which could enhance the strength of the interface. The density functional theory calculations show that the decohesion energy of silicon carbide-boron carbide (without intermixing) is smallest at the interface as compared with the bulk silicon carbide and boron carbide, and that the structure would fail along the interface.

中文翻译：

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微观结构和界面在控制固态制造纳米复合材料机械性能中的作用

已经做出了相当大的努力来制造低密度复合材料，并通过添加碳化硼颗粒来提高金属和合金的比强度。提高这些复合材料机械性能的主要因素之一是金属/陶瓷界面的界面特性，特别是金属/陶瓷界面之间的结合强度。在这里，我们使用透射电子显微镜研究了在相对高压下以固态加工的碳化硼 - 镍 (B4C-Ni) 和碳化硅 - 碳化硼 (SiC-B4C) 复合材料的微观结构和界面特性。烧结碳化硼和镍粉表现出改善的硬度和模量，这归因于在镍 - 碳化硼界面处形成硼化镍 (Ni4B3)。使用细探针能量色散光谱和高角度环形暗场成像，我们观察到碳化硅-碳化硼界面的富硅混合层，这可以增强界面的强度。密度泛函理论计算表明，与块状碳化硅和碳化硼相比，碳化硅-碳化硼（无混合）在界面处的脱聚能最小，并且结构会沿界面失效。