- Nana Ofori-Opoku, Northwestern University, Evanston, Illinois
The compromise between kinetic and thermodynamic processes gives rise to the rich patterns exhibited in materials microstructure. The resultant, often, nonequilibrium patterns and structures ultimately determine the various properties exhibited by materials. In this talk, I will use two classes of problems as paradigms for nonequilibrium microstructural formations, each examined at different length scales. First, at the mesoscale, I will discuss ongoing work in solidification under additive manufacturing conditions. To maintain fidelity with relevant conditions, the solidification conditions are taken from a finite element treatment of the melt pool characteristics based on experimental conditions. Here we determine the characteristic length scales of the columnar patterns that form and their steady-state behavior. Secondly, resolving atomic-scale processes, we will look at the initial stages of cluster and precipitation reactions in models developed to mimic Al alloys. We explore the role of defects in the clustering process and find that quenched-in defects are essential to the nucleation process. Corroborated by experiments, we determine that the nucleation process can be defect mediated. Lastly, looking forward, I will discuss the development of an emergent suite of models that aim to bridge the disparate length scales between the classes of model discussed.