Multiscale Simulation and Experimental Study of Thermotransport in Binary Alloys

技术概要：当金属合金中存在大的温度梯度时，可能发生成分梯度和相变，潜在地导致机械故障或不期望的性质变化。这种效应被称为热输运，在固体的原子尺度上还没有得到很好的理解。目前，还没有理论方法来预测相关的传输参数。PI建议使用相场模型结合基于原子尺度模拟（包括分子动力学和动力学蒙特-卡罗模拟）的多尺度计算方法来阐明热传输。为了计算关键的输运参数，将计算在温度梯度存在下空位扩散的局部自由能分布。这种方法可以直接计算与运输有关的耗散过程。理论预测将使用Cu-Ni和Ni-Al二元合金的实验结果进行验证。非技术性总结：在与许多应用相关的材料中，包括核燃料合金、电子电路互连和燃气涡轮发动机合金，不断追求更高的效率、更高的温度和更小的尺寸导致操作期间非常大的温度梯度。由于大的温度梯度，组成原子倾向于重新分布，导致组成梯度和相变。这种效应被称为热传递，导致工程组件的性能变化。例如，涡轮机叶片中的成分重新分布可导致机械故障。在这个项目中，PI将使用模拟在原子和连续尺度，沿着与实验，阐明在Ni-Al和Cu-Ni二元合金的热输运。预测和理解热输运的能力预计将对高温环境中使用的合金的稳定性产生重大影响。博士学生将接受实验和计算研究的培训。计算工具将提供给全州佛罗里达材料模拟学会的学生。将为K-12学生和教师举办一个夏季“材料营”，其中包括来自科学职业中代表性不足的群体的学生。结果将提供给社区，并集成到商业软件包中，用于模拟多组分合金中的扩散。

TECHNICAL SUMMARY: When large temperature gradients are present in metallic alloys, compositional gradients and phase transformations can occur, potentially leading to mechanical failure or undesirable changes in properties. This effect, known as thermotransport, is not well understood at the atomic scale for solids. Currently, there are no theoretical approaches to predict the relevant transport parameters. The PIs propose to elucidate thermotranport using phase-field modeling in conjunction with a multiscale computational approach based on atomic-scale simulation that includes molecular-dynamics and kinetic Monte-Carlo simulations. To compute key transport parameters, the local free energy profiles for vacancy diffusion in the presence of a temperature gradient will be computed. This approach enables direct computation of dissipative processes relevant to transport. Theoretical predictions will be validated using the results of experiments on Cu-Ni and Ni-Al binary alloys.NON-TECHNICAL SUMMARY: In materials relevant for many applications, including nuclear-fuel alloys, interconnects for electronic circuits, and alloys for gas-turbine engines, the relentless drive towards higher efficiencies, increased temperatures, and smaller dimensions results in very large temperature gradients during operation. As a result of large temperature gradients, constituent atoms tend to be redistributed, leading to composition gradients and phase transformations. This effect, known as thermotransport, results in property changes in engineered components. For example, constituent redistribution in turbine blades can lead to mechanical failure. In this project, the PIs will use simulation at the atomic and continuum scales, along with experiments, to elucidate thermotransport in Ni-Al and Cu-Ni binary alloys. The ability to predict and understand thermotransport is expected to have a major impact on the stability of alloys used in high-temperature environments. Ph.D. students will be trained in the experimental and computational studies. Computational tools will be accessible to students in the statewide Florida Society for Materials Simulation. A summer 'Materials Camp' for K-12 students and teachers, including students from groups under-represented in science careers, will be hosted. The results will be made available to the community and integrated into commercial software packages for the simulation of diffusion in multicomponent alloys.