Time-of-flight neutron double Bragg reflection at small scattering angle. A new tool for structural investigations of materials

The subgrain structure of a single crystal and its evolution under mechanical loading have been investigated non-destructively by a novel technique of combining the neutron time-of-flight method with the detailed analysis of double Bragg reflections at small scattering angle (DBR-SANS). The in situ measurements were performed for single crystals of Pb, Cu and Al at room temperature. The slight change of the structure is deduced by modelling the measured intensities and the line broadenings of the reflection peaks in terms of a DBR-SANS intensity formula derived on the basis of the kinematical diffraction theory. The angular correlation in orientation of mosaic subgrains and the associated slip deformations are described and discussed. The critical resolved shear stresses are evaluated. (orig.)