Influence of heterogeneous dislocation arrangements on X-ray diffraction profiles measured on cyclically deformed nickel single crystals. Pt. 1. Profile broadening at different plastic strain amplitudes

X-ray diffraction profiles of Bragg reflections were measured on cyclically deformed nickel single crystals of different orientations with a high-resolution double crystal diffractometer. The mesoscopic dislocation structures beneath the crystal surfaces were studied by scanning electron microscopy using the channelling contrast of backscattered electrons. Changes of internal stresses on different length scales can be inferred from the characteristic dependence of the diffraction profile broadening on the plastic strain amplitude. Short-range stresses are predominant in the matrix structure of crystals cyclically deformed at small strain amplitudes. At higher amplitudes, in the plateau region of the cyclic stress-strain curve, remarkable long-range stresses arise in crystals of all orientations due to the existence of ladder-like, cellular and other dislocation structures. (orig.)