Nb-Si系超高温金属间化合物的微观组织结构与控制

项目名称： Nb-Si系超高温金属间化合物的微观组织结构与控制

项目编号： No.50871005

项目类型： 面上项目

立项/批准年度： 2009

项目学科： 金属学与金属工艺

项目作者： 韩雅芳

作者单位： 北京航空航天大学

项目金额： 39万元

中文摘要： 本项目采用粉末冶金、电弧熔炼和定向凝固等方法制备了不同组织结构的模型材料，采用SEM、TEM、XRD、EDS、EPMA 等分析技术研究了不同制备工艺、合金化元素对材料组织和性能的影响；分析了第二相体积分数、尺寸、分布、形态对材料性能的影响以及对铌基固溶体相和铌硅化物相的界面结构进行了研究。结果表明不同的制备方法对材料的组织和性能明显，其中定向凝固法和激光快速成型法通过优化工艺参数，可以控制微观组织结构，破坏熔炼过程中的大块硅化物，获得均匀细化的组织；合金化元素Zn的加入，打破了第二相硅化物的网状连接，抑制了部分颗粒状硅化物的析出，延缓了断裂过程中的裂纹扩展，有效地提高了合金的室温韧性；P的加入促进了第二相硅化物Nb3Si向Nbss/Nb5Si3的转变；研究表明第二相的以弥散的颗粒或共晶团形式分布在Nbss内，对合金综合性能的提高最有利；Nb-Si系合金中铌基固溶体和铌硅化物相的界面结构较平直洁净，两相间没有发现确定的取向关系；控制合金熔炼过程和凝固过程中的组织演化可以通过改变定向凝固过程中的旋转方式来实现。

中文关键词： 金属间化合物；Nb-Si系；微观组织；界面结构；力学性能

英文摘要： With their high melting point, moderate density, excellent strength at high temperature, good room temperature fracture toughness and intrinsic thermodynamic stability, Nb-Si based ultra-temperature intermetallics have been regarded as a promising candidate to replace the Ni-based superalloys used for the next generation aircraft engines at 1100-1400℃Nb-Si based Ultra-temperature intermetallics with different microstructures have been prepared using different processing methods of arc melting with non-consumable tungsten electrode, directional solidification and Laser Rapid Prototyping. Effect of processing methods and alloying elements on microstructure and properties of Nb-Si superalloys was analysed by SEM, TEM, XRD, EDS and EPMA.And the influence of the volume fraction, size, distribution, and morphology of secondary phase on mechanical properties of Nb-Si based superalloys and the interfacial structure between Nbss and Nb-Silicide were also researched.The results showed that the microstructure of Nb-Si based alloys could be controlled by different processing methods. The finer microstructure can be obtained by laser rapid prototyping method. And in the processing of melting, the bulk Nb-silicide could be destructed by directional solidification.With the addition of Zn, the network structure of the secondary phase was broken and some particles of Nb-silicide were inhibited so that the room temperature fracture toughness was improved.And the addition of P promoted the secondary phase Nb3Si transformed into Nbss/Nb5Si3.The results also showed that the secondary phase in the form of particles and eutectic existing on Nbss was benefit to improve the properties of Nb-Si alloys.The interface between Nbss and Nb-Silicide was relatively straight and clean and there was no orientation relationship between the two phases.

英文关键词： Intermetallics；Nb-Si based；Microstructure；Interfacial structure；Mechanical property