Local Deformation Mapping Reveals Diffusion through Microstructures

Abstract Understanding and quantifying microstructure–property relationships, particularly those where plastic deformation is based on atomic diffusion, remains a grand challenge in metallurgy. While existing techniques often tradeoff between spatial resolution, sampling area, and throughput, a method capable of bridging various length scales remains elusive. To address this need, we propose local deformation mapping (LDM) as a high-resolution, high- throughput characterization technique. LDM determines what diffuses locally through microstructures, creating a direct deformation map imprinted on top of the microstructure. These maps can exhibit ~10 nm² resolution across macroscopic areas (~cm²), generating up to ~10¹² data points in a single experiment. This technique maps deformation-related properties such as diffusivity as a function of microstructural features, including grains, grain boundaries, and interphase boundaries. 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. Experimentally, LDM is realized by pressing a nanomold onto a microstructure, inducing local stress gradients that drive material from the microstructure into mold pores, forming nanorods. This spatial separation of the plastic response from the microstructure enables sensitive chemical composition mapping of this flux in multicomponent microstructures, previously unachieved with the state of the art. Nanorods’ length and composition form the deformation response maps, converted into diffusivity maps via the hereby developed analytical model. 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.