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.

由于多组分合金体系和多相沉淀，单晶（SC）高温合金凝固过程中的微观结构形成非常复杂。在我们的初步研究工作中，发现并证明了γ/γ′共晶可能是由熔体枝晶间区域的γ枝晶单独产生的，因此具有随机的晶体取向。在添加碳的超级合金中，大多数γ/γ′共晶优选在熔体中现有的碳化物上成核，因此也根据其碳化物基体的取向而显示出随机取向。因此，所谓 SC 铸件的微观结构实际上是多晶的，尽管无法检测到宏观晶界。在该项目中，将系统地研究单晶凝固高温合金中的多相凝固和由此产生的多晶微观结构，因为它对于基础研究和工业应用都具有重要意义。将研究高度错误取向的共晶的成核行为，以解释为什么共晶优选从熔体中甚至在具有非常不同的晶格的碳化物上成核，并且不容易在具有大致相同的晶格参数的现有γ枝晶上成核。最后，开发和建立了一个模型概念，描述高温合金中伽马/伽马素共晶的凝固。基于该模型，我们将尝试通过改进凝固过程来避免或至少显着减少这种取向错误缺陷，以获得更好的微观结构单晶度和最佳的超临界铸件质量。