In-situ tracking the structural and chemical evolution of nanostructured CuCr alloys

We report the thermal stability of supersaturated CuCr nanocrystallines alloys at the atomic resolution using modern spherical aberration-corrected transmission electron microscopy (TEM) via performing in-situ structural and spectroscopy experiments. It is found that CuCr nanocrystallines are not only subjected to a structural change but also undergo a chemical evolution upon annealing. Chemical destabilization of supersaturated CuCr nanocrystallines occurs at a quite low temperature. Heating triggers a rapid separation of Cu and Cr grains at the forced intermixing zone, accompanied by an obvious decrease of average interface width whereas the grain growth is not significant. Elemental profiles and images recorded in real time reveal that the local compositions vary with heating, which in turn permits to derive the concentration of excess vacancy generated by deformation and observe its evolution with temperature, further to analyze the dynamic behavior in nanocrystalline materials. Electronic structure changes at the interface forced intermixing zone are revealed by the fine structure analysis. The study uncovers the interplay between the thermal stability and chemical decomposition process of bulk nanostructured materials in real-time.

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