Three-dimensional tomographic characterization of nanostructures in aluminum alloy multilayers by small- and wide-angle X-ray scattering

In order to enhance the performance and reliability of aluminum-based functionally graded materials (FGMs), it is essential to understand the spatial distribution of nanoscale precipitates and their influence on mechanical properties. In this study, Small-Angle X-ray Scattering Computed Tomography (SAXS-CT) and diffraction CT were applied to visualize and quantify the three-dimensional distribution of nanoscale precipitates and crystallographic orientations in Al–Zn–Mg multilayer plates with compositional gradients. The analysis revealed a clear correlation between the distribution of Guinier radius, integrated scattering intensity, and Zn/Mg content, suggesting aging-dependent structural evolution and localized reversion phenomena in Zn-rich regions. The integration of Vickers hardness tests with SAXS-CT-derived structural parameters facilitated the prediction of local hardness through the application of Orowan and cut-through strengthening models. Furthermore, integration of the Schmid factor derived from diffraction CT allowed the construction of a yield strength map, identifying grains more prone to yielding. In conclusion, three-dimensional SAXS-CT of a three-layer sample with greater thickness confirmed nanoscale structural transitions along the gradient. This study demonstrates the potential of SAXS-CT as a powerful, non-destructive technique for guiding the microstructural design and mechanical optimization of aluminum-based FGMs.