Analyse von Bragg-Beugungsprofilen zur Charakterisierung der Mikrostruktur und des Verformungsverhaltens von ein- und vielkristallinem Nickel (English shop)

Preview

Table of Contents, Datei (51 KB)
Preface, Datei (32 KB)
Extract, Datei (120 KB)

The major challenge in analysing Bragg diffraction profiles for characterising the microstructure and deformation behaviour of plastically deformed fcc metals lies in appropriately adapting the evaluation algorithms to the conditions of the real structure. The proposed concept for diffraction profile analysis takes into account the deformation-induced heterogeneous dislocation arrangement on different length scales and can be applied to investigations ranging from the single crystal to the nanocrystalline polycrystal (mean grain size ≥100nm). The progress achieved consists in particular in the mutually independent determination of long-range residual stresses at the macroscopic, crystalline and mesoscopic structural levels, of “local” dislocation densities at a mesoscopic structural level, as well as of characteristics of the grain structure.

This concept was applied to high-resolution measurements of Bragg diffraction profiles obtained on nickel single crystals and polycrystals after unidirectional and cyclic plastic deformation over a wide temperature range. This made it possible to provide experimental evidence for and quantitative determination of spectra of long-range residual stresses at different structural levels, which are an expression of inhomogeneous plastic deformation, as well as to reveal relationships between local stress, local dislocation density and geometrical structural parameters of the dislocation arrangement. In addition, insights were gained into the influence of grain size on the evolution of the microstructure and on the dominant deformation mechanisms during unidirectional and cyclic plastic deformation in fcc metals.