Local deformation mapping reveals diffusion through microstructures.

Abstract

Microstructure-property relationships, particularly those where plastic deformation is based on atomic diffusion, remain a grand challenge in metallurgy due to the tradeoff between spatial resolution, sampling area, and the associated throughput. To address this, we propose local deformation mapping (LDM) as a high-resolution, high-throughput characterization technique. LDM determines what diffuses locally through microstructures, experimentally realized by pressing a nanomold onto a microstructure, forming a nanorod array. Such arrays, representing deformation maps, can exhibit ~10 nm² resolution across macroscopic areas ( ~ cm²), generating up to ~10¹² data points in a single experiment. The spatial separation of the plastic response from the microstructure enables sensitive chemical composition mapping of this response. Nanorods' length and composition are then converted into diffusivity maps via a hereby developed analytic model. We demonstrate a one-step determination of grain boundary diffusivity as a function of misorientation angle, temperature-dependent deformation behavior, and previously unknown fast diffusion within interphase boundaries in eutectic-containing alloys. Altogether, LDM is a powerful platform to advance the quantitative understanding of structure-property relationships for a wide range of materials across a broad temperature range.