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Directional solidification of multiphase metallic high temperature materials beyond Ni-base superalloys

镍基高温合金以外的多相金属高温材料的定向凝固

基本信息

批准号：
171451837
负责人：
Professor Dr.-Ing. Martin Heilmaier
金额：
--
依托单位：
Institut für Angewandte Materialien - Werkstoffkunde (IAM-WK)
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2010
资助国家：
德国
起止时间：
2009-12-31 至 2017-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/171451837?language=en
关键词：
Directional solidification multiphase metallic temperature

项目摘要

Major goal of this project is to determine the influence of directional solidification (DS) on the mechanical properties of alloy systems exhibiting melting points far beyond Nickel based superalloys (e.g. Nb-Si-Cr and Mo-Si-Ti). As soon as the zone melting device had been put into service by using the reference binary eutectic alloy Nb-18 at% Si, the obtained knowledge was transferred to the three-phase system Nb-Si-Cr and to the two-phase system Mo-Si-Ti. A direct correlation between solidification parameters and the resulting microstructure was obtained. Regarding the high temperature creep properties, DS of Nb-18 at% Si led to a significantly increased creep resistance (about three orders of magnitude better), as compared to a powder metallurgically produced alloy. This difference can mainly be attributed to the different size of microstructural features, the predominant mechanism being diffusional creep in both materials. A comparison with a state of the art single-crystalline Nickel based superalloys (CMSX 4) underpins the outstanding improvement of the creep resistance of DS NbSi eutectics. First creep results for DS ternary Nb-Si-Cr alloys indicate dislocation creep to be the rate controlling mechanism. The observed increase of the stress exponent with decreasing stress can be rationalized by the formation of nanoscaled NbCr2 precipitates. Unexpectedly, the arc melted reference alloy, exhibits superior creep resistance. In the second phase of the project, phase field simulations will be continued at the binary Nb-Si in 3D, involving anisotropic interfacial energies derived from atomistic models. Through simulation studies, an understanding of the spatial composition of the lamellar structure is obtained in 3D and the influence of potential nucleation events is analyzed. In parallel, a deeper understanding of the creep behavior observed in the ternary system Nb-Si-Cr will be developed. Also, the determination of the ductile-brittle transition temperature (DBTT) and the oxidation properties is a major task of this project. Besides experimental identification of the ternary-eutectic point, the phase field modelling will be extended to the ternary Nb-Si-Cr system. For two thermodynamic models based on Pandat data and on experimental results, 3D microstructure simulations will be performed. Phase arrangements and microstructural parameters will be comparatively assessed, and the morphologies will be categorized. Based on own literature data, the alloying element Vanadium will be added to the Nb-Si-Cr system, as it potentially improves fracture toughness and oxidation resistance. In the system Mo-Si-Ti an optimum composition regarding the possibility of directional solidification, has to be identified. Finally, selected creep tests will be performed to compare the influence of the generated microstructures.

该项目的主要目标是确定定向凝固（DS）对合金系统机械性能的影响，这些合金系统的熔点远远超过镍基高温合金（例如Nb-Si-Cr和Mo-Si-Ti）。区域熔炼装置以参考二元共晶合金Nb-18在% Si的情况下投入使用后，所获得的知识被转移到三相体系Nb-Si-Cr和两相体系Mo-Si-Ti。得到了凝固参数与凝固后的微观组织之间的直接关系。在高温蠕变性能方面，与粉末冶金生产的合金相比，在% Si下添加Nb-18的DS显著提高了抗蠕变性能（大约提高了三个数量级）。这种差异主要是由于两种材料的微观组织特征尺寸不同，其主要机制是扩散蠕变。与最先进的单晶镍基高温合金（cmsx4）相比，DS NbSi共晶材料的抗蠕变性能得到了显著改善。对DS三元Nb-Si-Cr合金的蠕变结果表明位错蠕变是控制蠕变速率的机制。应力指数随应力减小而增大的现象可以通过纳米NbCr2析出物的形成来解释。出乎意料的是，电弧熔化的基准合金，表现出优异的抗蠕变性能。在该项目的第二阶段，将继续在二元Nb-Si的三维中进行相场模拟，涉及从原子模型中导出的各向异性界面能。通过模拟研究，获得了三维层状结构的空间组成，并分析了潜在成核事件对层状结构的影响。同时，对Nb-Si-Cr三元体系中观察到的蠕变行为的更深层次的理解将得到发展。同时，确定材料的韧脆转变温度（DBTT）和氧化性能是本课题的主要工作。除了三元共晶点的实验识别外，相场建模将扩展到三元Nb-Si-Cr体系。对基于Pandat数据和实验结果的两个热力学模型进行了三维微观模拟。相排列和微观结构参数将进行比较评估，并对形貌进行分类。根据自己的文献数据，将合金元素钒添加到Nb-Si-Cr体系中，因为它有可能提高断裂韧性和抗氧化性。在Mo-Si-Ti体系中，必须确定定向凝固可能性的最佳成分。最后，将进行选定的蠕变试验，以比较产生的微观结构的影响。