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.