Phase equilibria data from ternary Cr-Nb-X (X = Hf, Ta, Ti, Zr) systems are relevant to the development of Niobium-silicide based composites for use in jet engines. Such systems present at several temperatures a pseudo-binary of Cr2Nb-Cr2X Laves phases. This work presents the experimentally determined liquidus projection and the 1200 °C isothermal section for the Cr-Hf-Nb system based on microstructural characterization of as-cast and heat-treated alloys. The microstructural characterization using x-ray diffractometry, scanning electron microscopy and electron probe microanalysis showed four eutectic-type monovariant reactions and two class II invariant reactions in the liquidus projection. The 1200 °C isothermal section showed complete solubility between Nb and Hf in (C15) phase and one three phase equilibria field.

中文翻译：

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Cr-Hf-Nb 系统的实验研究：液相线投影和 1200 °C 等温截面

来自三元 Cr-Nb-X（X = Hf、Ta、Ti、Zr）系统的相平衡数据与用于喷气发动机的铌硅化物基复合材料的开发有关。这种系统在几个温度下呈现 Cr2Nb-Cr2X Laves 相的伪二元。这项工作基于铸态和热处理合金的显微结构表征，展示了实验确定的液相线投影和 Cr-Hf-Nb 系统的 1200 °C 等温截面。使用 X 射线衍射、扫描电子显微镜和电子探针微量分析的微观结构表征表明，液相线投影中有四种共晶型单变反应和两种 II 类不变反应。1200 °C 等温截面显示 Nb 和 Hf 在 (C15) 相和一个三相平衡场中完全溶解。