To investigate the morphological evolution of the NbC phase, a niobium-cast iron diffusion couple was designed and fabricated. The two-dimensional (2D) and three-dimensional (3D) growth morphology of NbC particles were analysed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The morphological evolution mechanism of NbC particles was also discussed. The results reveal that from the interface of the Nb wire/NbC-Fe diffusion layer to the cast iron, as the thickness of the NbC-Fe diffusion layer increases, the morphology of NbC particles changed from the nearly spherical to truncated cube, then to a perfect cube. The evolution of particle morphology is mainly attributed to the change in the C/Nb ratio and the existence of Fe atoms affecting the relative growth rates of the {111} and {100} facets on a NbC crystal.

中文翻译：

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铌铁扩散偶界面处 NbC 颗粒的形态演变

为了研究 NbC 相的形态演变，设计并制造了铌-铸铁扩散偶。使用扫描电子显微镜 (SEM) 和透射电子显微镜 (TEM) 分析了 NbC 颗粒的二维 (2D) 和三维 (3D) 生长形态。还讨论了 NbC 颗粒的形态演化机制。结果表明，从 Nb 丝/NbC-Fe 扩散层到铸铁的界面，随着 NbC-Fe 扩散层厚度的增加，NbC 颗粒的形貌由近球形变为截头立方体，再到一个完美的立方体。颗粒形貌的演变主要归因于 C/Nb 比的变化和 Fe 原子的存在影响 NbC 晶体上 {111} 和 {100} 面的相对生长速率。