Multiphase Solidification and Multi-crystal Microstructure in Single Crystal Superalloys

单晶高温合金中的多相凝固和多晶微观结构

• 批准号: 396638945
• 负责人: Professor Dr.-Ing. Andreas Bührig-Polaczek
• 金额: --
• 依托单位: Gießerei-Institut (GI)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/396638945?language=en
• 关键词: Multiphase; Solidification; Multi; crystal; Microstructure

The microstructure formation during solidification of single-crystal (SC) superalloys is complex due to the multicomponent alloy system and the multiphase precipitation. In our preliminary research work it was found and demonstrated that the gamma/gamma-prime eutectic may arise from the gamma dendrites in the interdendritic region of the melt separately and thus has a random crystal orientation. In superalloys with carbon additions, most of the gamma/gamma-prime eutectics preferably nucleate on the existing carbides in the melt, thus also revealing random orientations as according to the orientation of their carbide substrates. As a result, the microstructure of the so-called SC castings is, in reality, polycrystalline, although no macroscopic grain boundaries can be detected. In this project, the multiphase solidification and the resulting polycrystalline microstructure in single-crystal solidified superalloys will be systematically investigated since it is of great importance to both fundamental research and industrial applications. The nucleation behavior of the highly misoriented eutectics will be studied to explain why the eutectics preferably nucleate from the melt or even on carbides having very different crystal lattices, and do not easily nucleate on the existing gamma-dendrites, which have approximately the same lattice parameters. Finally, a model concept is developed and build-up that describes the solidification of gamma/gamma-prime eutectics in superalloys. Based on this model, attempts will be made to avoid or at least significantly reduce this misorientation defect by improving the solidification process, with the aim of obtaining a better microstructural monocrystallinity and an optimal quality of the SC castings.

单晶高温合金由于存在多元合金体系和多相析出，凝固过程中组织形成复杂。在我们的初步研究工作中，我们发现并证明了伽马/伽马初生共晶可能分别来自熔体枝晶间区的伽马枝晶，从而具有随机的晶体取向。在添加碳的高温合金中，大多数伽马/伽马素共晶优先在熔体中现有的碳化物上形核，因此也根据其碳化物基体的取向显示出随机取向。因此，所谓的SC铸件的微观组织实际上是多晶的，尽管无法检测到宏观晶界。本课题对单晶高温合金的多相凝固及其多晶组织进行了系统的研究，具有重要的基础研究和工业应用价值。将研究高度错位共晶的形核行为，以解释为什么共晶优选从熔体甚至在具有非常不同晶格的碳化物上形核，而不容易在具有大致相同晶格参数的现有伽马枝晶上形核。最后，发展和建立了描述高温合金中伽马/伽马素共晶凝固的模型概念。基于这一模型，将试图通过改进凝固工艺来避免或至少显著减少这种取向不良缺陷，目的是获得更好的组织单晶性和最优的SC铸件质量。