Nb/Mo-Si基超高温材料体系的相关系与合金化研究

The Nb/Mo-based alloys may consist of co-existed phases to improve the room-temperature toughness, the high-temperature strength, and the oxidation resistance, respectively. The reasonable match of these constituent phases can make the high-temperature components of the jet engines run hotter and more efficiently. In the train of the recent research, which focuses on the development of the materials composed of multi-components and co-existed phases, the fundamental investigation on the related phase equilibria, thermodynamics and alloying principles is becoming a more and more active demand. In the present project, the Mo-Nb-Si-X (X=B,Cr,Hf/W) systems are typically concerned. On the basis of the phase equilibrium measurement and the thermodynamic assessment, the interested thermodynamic database will be developed. Furthermore, the theoretical prediction and the experimental study on the highly stable microstructure of the co-existed multi-phases will be carried out. The systematic and deepening analysis for the Nb/Mo-Si based high temperature materials will be concentrated on the optimum combination and interaction influence of the alloying elements, as well as on the effective formation and transformation evolution of the in-situ microstructure, to promote toughening, strengthening and anti-oxidation ability. As a result, the close correlation between the analysis of phase equilibria and the design of phase constituents can be obtained. The further investigation is expected to provide the experimental data and scientific basis for the related alloy design, microstructure control and process optimization of the multi-components Nb/Mo-Si based high temperature materials.

以铌或钼为基的合金可同时包含室温增韧相、高温增强相、抗环境氧化相等，其中各组成相的合理匹配能使喷气式发动机的高温部件在更高的温度下以更高的效率运行。目前的研究重点正朝着多元复相材料体系的方向发展，随之对相关的相平衡关系、相图热力学和合金化原理等基础信息提出了迫切的需求。本项目将重点针对Mo-Nb-Si-X(X=B,Cr,Hf/W)多元合金体系，通过相平衡实验和热力学优化，建立热力学数据库。并在此基础上，开展高稳定性多相平衡共存组织的理论预测与实验研究。系统深入地分析Nb/Mo-Si基超高温合金体系中可供协同调控增韧、增强、抗氧化的合金元素优化组合和相互作用影响程度，以及原位获得理想微观结构的有效形成条件和组织演化规律，取得相平衡计算和相组成设计的紧密关联。进而为开展Nb/Mo-Si基多元超高温合金材料的合金设计、组织控制和工艺优化等提供必要的相平衡实验数据和热力学理论基础。

本项目重点针对Nb/Mo-Si基超高温合金构成的Mo/Nb-Si-X（X=Al, Cr, Hf, Ti, V, W）二元及三元系（包括Mo-V、Nb-V、Mo-Nb、Hf-Si、Mo-Nb-V、Nb-Si-V、Mo-Si-V、Hf-Mo-Si、Al-Mo-Si、Al-Nb-Si、Cr-Mo-Si、Cr-Nb-Si等），开展相平衡实验测定和热力学优化评估。在此基础上，系统研究合金元素在室温增韧相、高温增强相、抗环境氧化作用相中的溶解度及其随温度和成分的变化、多相稳定共存的成分-温度范围、以及不同成分合金体系的相平衡、相组成、组织演化规律等，进而为开展Nb/Mo-Si基多元超高温合金材料的合金设计、组织控制和工艺优化等提供必要的相平衡实验数据和热力学理论基础。. 研究发现Mo-V和Nb-V二元系低温区存在的固态溶解度间隙。采用合金法、扩散偶法、差热分析法、扫描电子显微镜和透射电子显微镜等方法，分别对Mo-V、Nb-V、Mo-Nb-V体系的等温平衡成分、界面平衡关系、相转变温度、显微组织形貌、相分解机制（调幅分解和形核长大）等进行了综合的测定和分析，并利用CALPHAD方法，通过建立合理的热力学模型，优化评估了Nb-V、Mo-V、Mo-Nb-V体系的热力学数据，进而确定了Bcc相在低温下出现溶解度间隙和调幅分解的温度-成分区间。针对合金元素V和Hf分别与Nb-Si和Mo-Si构成的Nb-Si-V、Mo-Si-Hf及Mo-Si-V三元系，设计并进行了不同成分合金的液固转变及相平衡实验。通过对合金凝固路径和等温平衡相关系的合理分析，确定了Nb-Si-Hf、Mo-Si-Hf及Mo-Si-V三元系的液相面投影图和等温截面图。优化获得了相应体系的热力学特征参数，结合文献报道的Nb-Si-Hf三元系热力学参数，构建了Nb-Mo-Si-V和Nb-Mo-Si-Hf四元系热力学数据库。. 本项目的前期工作研究了Mo-Nb-Si-Ti和Nb-Si-Ti-W四元系，当前工作仍在研究Mo-Nb-Si-Al和Mo-Nb-Si-Cr四元系，结合本项目研究的Nb-Mo-Si-V和Nb-Mo-Si-Hf四元系，有望构建一个Mo-Nb-Si基多元体系热力学数据库。将相平衡计算和相平衡设计紧密关联，进而为超高温合金结构材料的合金设计，组织控制和工艺优化提供有力的实验数据及理论基础。