中文摘要：

Nb-Si基共晶体系超高温合金是目前最有希望应用于超高温环境的材料之一。目前的研究还仅仅停留在合金化改善其综合性能及抗氧化涂层的制备等方面，而对其共晶凝固机理等更深层次的研究还较少。从Nb基超高温合金铸态、定向凝固态组织及相组成等角度入手对该合金的微观组织变化规律进行了分析和总结；并对Nb基超高温合金共晶凝固机理的研究进展进行了综述；此外，还讨论了该合金目前仍需解决的问题。

英文摘要：

The Nb-Si based eutectic ultra-high temperature alloy is one of the most promising materials for the very-high temperature structural applications. Up to now, much effort has been made to evaluate the influence of alloying elements on the environmental and mechanical properties and to prepare the oxidation-resistant coatings, but few researches have been conducted on the directional solidification theories of this eutectic system. In this paper, a review of the microstructure evolution of both arc-melted and directionally solidified niobium based uhrahigh temperature alloys is presented. The eutectic solidification mechanism of the niobium based alloy is also summarized in the aspects of primary phase formation and the influence of solidification rates on the microstructure selection. Furthermore, the prospective research effort about this alloy is put forward.