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We report the measurements of in situ Debye–Scherrer x-ray diffraction from copper foils shock compressed at the Orion laser facility to pressure in the range of 10–40 GPa. Our objective was to record distortion (variation of scattering angle at peak intensity, 2θ, with azimuthal position, φ, around the diffraction ring) of the Debye–Scherrer rings. We intended to measure the anisotropy of elastic strain and infer the effective strength of copper at a high strain rate. However, our measured diffraction data from all crystallographic reflection planes considered together are not consistent with a simple model that assumes homogeneous elastic strain. Consideration of both the β-fiber metallurgical texture of the rolled copper foil that we used as the sample material and the measured diffraction linewidths provides an empirical understanding of the data. We extend our understanding by using a Taylor-type, single-crystal plasticity model in which the total strain of each grain is assumed to be identical to that of the whole sample. This model reproduces many features of our experimental data and points to the importance of accounting for the plastic anisotropy of single-crystal grains, which can, in turn, lead to inter-grain elastic strain inhomogeneity and complex distortions of the diffraction rings. [ABSTRACT FROM AUTHOR]

We report experiments in which powder-diffraction data were recorded from polycrystalline vanadium foils, shock-compressed to pressures in the range of 10-70 GPa. Anisotropic strain in the compressed material is inferred from the asymmetry of Debye-Scherrer diffraction images and used to infer residual strain and yield strength (residual von Mises stress) of the vanadium sample material. We find residual anisotropic strain corresponding to yield strength in the range of 1.2 GPa-1.8 GPa for shock pressures below 30 GPa, but significantly less anisotropy of strain in the range of shock pressures above this. This is in contrast to our simulations of the experimental data using a multi-scale crystal plasticity strength model, where a significant yield strength persists up to the highest pressures we access in the experiment. Possible mechanisms that could contribute to the dynamic response of vanadium that we observe for shock pressures ≥30 GPa are discussed. [ABSTRACT FROM AUTHOR]