High-Throughput Measurements for High-Fidelity Thermodynamic Databases

技术支持：采用CALPHAD（相图计算）方法的计算热力学是多元合金设计和优化中最重要的工具之一。然而，它的应用受到严重限制，缺乏准确的热力学数据库与广泛的元素覆盖面。高保真热力学数据库开发中的限速步骤是获得大量的实验数据输入，包括：（a）所有关键的三元相图;（B）晶体结构和零维（0 D）缺陷的知识，例如有序化、位置占据、位置偏好和组成点缺陷（空位、空位和反位），以便开发金属间相的最佳热力学模型;（c）比热容（CP）、生成热和相变的转变热;以及（d）作为组成的函数的磁转变温度和磁矩，以考虑磁对吉布斯自由能的贡献。该项目旨在开发强大的，高通量的工具，将彻底改变（c）和（d）的测量。该研究将把一种新兴的微尺度CP测量工具扩展到低温和高温，以实现CP随温度变化的局部测量。在相变温度范围内对CP进行积分可以用来计算相变热，这是另一个重要的热力学量。该研究还将利用磁光克尔效应和磁共振力显微镜开发精确的微尺度磁矩测量工具。通过使用这些工具对在扩散倍数中形成的固溶体和金属间相进行测量，可以高效率和高精度地获得有价值的数据，如依赖于温度和成分的CP和依赖于成分的磁矩，而无需制作单独的合金。这些数据与相图和从扩散倍数获得的0 D缺陷信息一起可以大大提高准确性并加速热力学评估，以扩展热力学数据库的元素覆盖范围。扩散多重技术和微尺度性质映射工具的发展将从根本上改变必要的实验数据的收集方式，以快速建立高保真的热力学数据库。从这些测量中产生的大量材料属性数据将大大提高我们增强材料设计，材料信息学和理解复杂材料行为的能力。此外，具有映射能力的微尺度工具构成了一套新的材料特性显微镜，可能会像SEM一样广泛使用，从而重塑未来进行实验材料研究的方式。该方案将帮助培训学生使用这些工具，并通过网络工具传播数据。非技术性：具有广泛元素覆盖范围的高保真热力学数据库将对合金设计产生巨大影响：1）减少试错实验，2）为动力学和性能建模提供热力学数据，3）减少通常需要测试合金对有害相形成的倾向的长期暴露实验。及时设计和插入高性能材料对美国经济的全球竞争力至关重要。

TECHNICAL: Computational thermodynamics using the CALPHAD (CALculation of PHAse Diagrams) approach is one of the most important tools used in multicomponent alloy design and optimization. Its applications are, however, severely limited by the lack of accurate thermodynamic databases with wide elemental coverage. The rate-limiting step in the development of high-fidelity thermodynamic databases is to acquire substantial experimental data inputs including: (a) all the key ternary phase diagrams; (b) knowledge of crystal structures and zero-dimensional (0D) defects such as ordering, site occupancy, site preference, and compositional point defects (vacancies, interstitials, and anti-sites) in order to develop best thermodynamic models for intermetallic phases; (c) specific heat capacity (CP), heat of formation, and heat of transition of the phases and phase transformations; and (d) magnetic transition temperature and magnetic moments as a function of composition to take into account the magnetic contribution to the Gibbs free energy. This project aims to develop robust, high-throughput tools that will revolutionize the measurements of (c) and (d). The research will extend an emerging micro-scale CP measurement tool to both low and high temperatures to enable localized measurement of CP as a function of temperature. Integration of CP over a phase transition temperature range can be used to evaluate the heat of transition which is another important thermodynamic quantity. The research will also develop accurate, micro-scale measurement tools for magnetic moments using both the magneto-optical Kerr effect and magnetic resonance force microscopy. By using these tools to perform measurements on solid solutions and intermetallic phases formed in diffusion multiples, valuable data such as temperature- and composition-dependent CP and composition-dependent magnetic moment can be obtained with high efficiency and high accuracy without making individual alloys. These data together with phase diagrams and 0D defect information obtained from diffusion multiples can greatly improve the accuracy and accelerate thermodynamic assessments to extend the elemental coverage of thermodynamic databases. The development of the diffusion-multiple technique and micro-scale property mapping tools will fundamentally change the way essential experimental data are gathered for fast establishment of high-fidelity thermodynamic databases. The tremendous amounts of materials property data generated from such measurements would greatly enhance our ability to augment materials design, materials informatics, and understanding of complex materials behaviors. Moreover, the micro-scale tools with mapping capabilities constitute a new suite of materials property microscopy that may become as widely used as SEM, thus reshaping the way experimental materials research is performed in the future. The program will help to training students to use these tools and disseminate the data via web-based tools. NON-TECHNICAL: High-fidelity thermodynamic databases with wide elemental coverage will have a tremendous impact on alloy design by: 1) cutting down the trial-and-error experiments, 2) providing thermodynamic data for kinetic and property modeling, and 3) reducing the long-term exposure experiments that are usually required to test the propensity of alloys against detrimental phase formation. The timely design and insertion of high-performance materials are critical to the global competitiveness of the U.S. economy.