Small-angle neutron scattering study of dislocations in deformed single-crystal copper

Small-angle neutron scattering measurements of deformed single-crystal copper have been performed over a wavevector transfer range of 0.0655 ≤ Q ≤ 1.32 nm⁻¹. The measurements included four samples deformed in compression at room temperature along the [110] direction to 6.8, 15.6, 35.0 and 54.3% reduction in thickness and an undeformed reference sample. The response of the reference sample followed the Porod law at lowest (Q and was, at least in part, the result of scattering from the external surfaces of the sample. The radially averaged net cross sections were found to increase with increasing deformation, while the power-law exponent n (dΣ/dΩ ∝ 1/Qⁿ) decreased from n ≃ 3 to n ≃ 2.2 with increasing deformation. The scattering response of the two most deformed samples was noticeably anisotropic. Analysis of this anisotropy revealed strong 1/Q² scattering perpendicular to the {111} dislocation slip planes, in agreement with the theoretical work of Seeger [J. Appl. Phys. (1959), 30, 629–637]. The decrease in the radially averaged power-law exponent is therefore attributed to strong 1/Q² behavior at the highest levels of deformation. Bulk-averaged edge dislocation densities that varied systematically from approximately 1 × 10¹⁰ to 5 × 10¹⁰ cm⁻² were obtained from the measured data.