Understanding materials microstructure and behavior at the mesoscale

Taking the mesoscale to mean length and time scales at which a material's behavior is too complex to be understood by construction from the atomistic scale, we focus on threedimensional characterization and modeling of mesoscale responses of polycrystals to thermal and mechanical loading. Both elastic and plastic internal structural responses are now accessible via high-energy x-ray probes. The combination of diffraction experiments and computed tomography, for example, is yielding new insights into how void formation correlates with microstructural features such as grain boundaries and higher-order junctions. The resulting large, combined data sets allow for validation of micromechanical and thermal simulations. As detectors improve in resolution, quantum efficiency, and speed of readout, data rates and data volumes present computational challenges. Spatial resolutions approach one micrometer, while data sets span a cubic millimeter. Examples are given of applications to tensile deformation of copper, grain growth in nickel and titanium, and fatigue cracks in superalloys.