Collaborative Research: Determination of Ni-Fe-Cr Species Dependent Transport Through Control of Temperature, Irradiation, and Grain Size

技术概述：Ni-Fe-Cr基面心立方合金(如镍基和奥氏体钢合金)经常被用作包括核反应堆在内的各种技术中的结构材料。Ni-Fe-Cr合金微结构演变的许多方面，特别是在辐照下，受点缺陷输运的控制，其物种相关性仍然知之甚少。在本项目中，提出了一种新的方法来确定Ni-Fe-Cr钢合金中与物种有关的扩散系数。它基于纳米晶体材料的辐射诱导偏析(RIS)的测量和建模。这项工作综合了多种方法来理解Ni-Fe-Cr和RIS中的点缺陷输运，包括晶粒度控制、RIS表征工具(STEM-EDS、聚焦离子束、透射电子显微镜和原子探针层析)以及基于从头计算的多尺度模型(包括团簇展开、动力学蒙特卡罗和速率理论模型)。这项工作将提供一个新的水平，以深入了解依赖于物种的Ni-Fe-Cr迁移的大小和机制，并为未来的微观结构建模提供信息。非技术摘要：Ni-Fe-Cr基钢经常作为结构材料用于包括核反应堆在内的广泛技术中。这些钢的长期可靠性的基本方面，特别是在辐照下，由镍、铁和铬扩散的方面控制，这些方面仍然知之甚少。PI建议将材料纳米技术和分子级计算机模拟的工具整合在一起，以提供对极端条件下镍、铁和铬在这些钢中如何运输的新层次的洞察。结果将被整合到更高级别的模型中，帮助预测钢材的可靠性和开发新材料。该项目将培训研究生和博士后研究人员在多个地点的团队中工作，并在材料表征、建模及其相互作用的基本领域工作。这项工作还将促进一些调查人员参与妇女参与核科学(WINS)组织和先进试验堆国家科学用户设施的活动。

TECHNICAL SUMMARY: Ni-Fe-Cr based fcc alloys (e.g., Ni-based and austenitic steel alloys) are frequently used as structural materials in a wide range of technologies, including nuclear reactors. Many aspects of Ni-Fe-Cr alloy microstructural evolution, particularly under irradiation, are controlled by point defect transport with species dependencies that are still poorly understood. In this project a novel approach to determine the species-dependent diffusion coefficients in Ni-Fe-Cr steel alloys is proposed. It is based on measurements and modeling of Radiation Induced Segregation (RIS) of nanocrystalline materials. The proposed work integrates multiple approaches to understanding point defect transport in Ni-Fe-Cr and to RIS, including grain size control, RIS characterization tools (STEM-EDS, Focused Ion Beam, TEM, and Atom Probe tomography), and multiscale ab initio based models (including cluster expansion, kinetic Monte Carlo and rate theory modeling). The work will provide a new level of insight into the magnitude and mechanisms of Ni-Fe-Cr species-dependent transport and inform future microstructural modeling.NON-TECHNICAL SUMMARY: Ni-Fe-Cr based steels are frequently used as structural materials in a wide range of technologies, including nuclear reactors. Essential aspects of the long-term reliability of these steels, particularly under irradiation, are controlled by aspects of Ni, Fe, and Cr diffusion that are still poorly understood. The PIs propose to integrate tools from materials nanotechnology and molecular-scale computer simulation to provide new levels of insight into how Ni, Fe, and Cr are transported in these steels under extreme conditions. The results will be integrated into higher levels models that aid in the prediction of steel reliability and the development of new materials. This project will train graduate students and postdoctoral researchers to work on a multi-location team and in fundamental areas of materials characterization, modeling, and their interaction. This work will also further the involvement by some of the investigators in the Women in Nuclear Science (WINS) organization and activities at the Advanced Test Reactor National Scientific User Facility (NSUF).