GOALI: Microalloying and Improvement of the Solidification Characteristics of Nickel-Base Single Crystals

碳的添加代表了一种很有前途的新方法，可以改善多种合金的凝固特性。然而，潜在的机制还没有被很好地理解。仔细控制碳和其他微合金化成分可能会对大型单晶成分的生产产生重大影响。该项目研究了这些添加剂对凝固液相线附近的斑点、偏析和析出过程的影响。用液态金属锡作为冷却剂，在Bridgman装置上进行了常规辐射冷却的定向凝固实验。利用偏析作图技术、差热分析和析出物的电化学提取，研究了合金化的作用。这项工作是在密歇根大学和通用电气公司(企业研究和开发公司，GE-CRD和通用电力系统公司，GE-PS)密切合作下进行的。此外，学生S将与GE-PS人员共同设计实验，并参观他们的工程和制造设施。这项研究对镍基高温合金单晶凝固的机理有了新的理解，以提高飞机发动机的性能和效率。这项研究将为学术人员和学生提供与业界同行互动的重要机会。

This project is aimed at greater understanding of the mechanisms responsible for the breakdown of single crystal solidification and their dependence on alloy chemistry of nickel-base superalloy single crystals that find technological applications in improving performance and efficiency of aircraft engines. Carbon additions represent a promising new approach to improving the solidification characteristics of a broad range of alloys. However, the underlying mechanisms are not well understood. Careful control of carbon and other microalloying constituents could have a substantial impact on the production of large single crystal components. The main goals of the project are to determine the influence of microalloying additions, including boron, zirconium, nitrogen, hafnium and magnesium that affect the carbide precipitation process, the liquidus temperature and partitioning of major elements during solidification. The project examines the influence of these additions on freckling, segregation during solidification and precipitation processes near the liquidus. Directional solidification experiments are conducted in a Bridgman apparatus with conventional radiation cooling and with the use of liquid metal tin as a coolant. The role of alloying is examined with the use of segregation mapping techniques, differential thermal analysis and electrochemical extractions of precipitates. The work is performed in close collaboration between University of Michigan and General Electric Company (Corporate Research and Development, GE-CRD and General Electric Power Systems, GE-PS). GE-CRD will provide support for an extended sabbatical visit of the co-P.I. to the University of Michigan, to facilitate the interaction with student(s) supported on the program. Additionally, student(s) will jointly design experiments with GE-PS personnel as well as visit their engineering and manufacturing facilities.This research develops new understanding of the mechanisms involved with solidification of nickel-base superalloy single crystals for improved performance and efficiency of aircraft engines. The research will lend significant opportunity for academic personnel and students to interact with industrial counterparts.