High-Throughput Measurements for High-Fidelity Thermodynamic Databases

技术：使用CALPHAD（相图计算）方法的计算热力学是多组分合金设计和优化中最重要的工具之一。然而，它的应用受到缺乏广泛元素覆盖的精确热力学数据库的严重限制。开发高保真热力学数据库的关键步骤是获得大量的实验数据输入，包括：(a)所有关键的三相图；(b)晶体结构和零维（0D）缺陷的知识，如有序、位占用、位偏好和组成点缺陷（空位、间隙和反位），以便开发金属间相的最佳热力学模型；(c)比热容（CP）、生成热、相和相转变的转变热；(d)磁转变温度和磁矩作为组分的函数，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，以彻底改变(c)和(d)的测量。该研究将新兴的微尺度CP测量工具扩展到低温和高温，使CP作为温度函数的局部测量成为可能。CP在相变温度范围内的积分可以用来计算相变热，相变热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、高精度地获得有价值的数据，例如与温度和成分相关的CP和与成分相关的磁矩，而无需单独制作合金。这些数据与从扩散倍数中获得的相图和0D缺陷信息一起可以大大提高热力学评估的准确性和速度，从而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基本实验数据的收集方式，从而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极大地增强我们增强材料设计、材料信息学和理解复杂材料行为的能力。此外，具有映射功能的微尺度工具构成了一套新的材料性质显微镜，可能会像扫描电镜一样广泛使用，从而重塑未来实验材料研究的方式。该项目将帮助培训学生使用这些工具，并通过基于网络的工具传播数据。非技术：具有广泛元素覆盖的高保真热力学数据库将通过以下方式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，以及3)减少通常需要测试合金对有害相形成倾向的长期暴露实验。高性能材料的及时设计和应用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.