Characterization of second-phase particles in metallic high-performance materials
Research output: Thesis › Doctoral Thesis
Particles have a strong influence on the properties of metallic high-performance materials. Therefore, their comprehensive characterization is of great importance. In this thesis a combined use of transmission electron microscopy (TEM), atom probe tomography (APT) and small-angle neutron scattering (SANS) was tested for applicability for differently heat-treated tantalum alloys and steels. The prior aim was to combine the results obtained by these methods in a way that allows characterizing all particles regarding their size distribution, shape, crystallography, composition, and volume fraction. While TEM and APT are direct-imaging methods, SANS is an indirect one. However, in comparison with TEM and APT, SANS allows analyzing significantly larger sample volumes, thus leading to a higher statistical relevance of the results. In the course of this thesis is has turned out that in case of ferromagnetic steel samples micromagnetic effects hinder the correct interpretation of SANS scattering data in terms of existing particles. It is shown that this limitation may be overcome by analyzing magnetic field dependent scattering data using an algorithm proposed in this thesis, since then the scattering contributions from particles and micromagnetic scattering can be separated. The data obtained in such a manner can be interpreted and combined with TEM and APT results in a correct way, which is an important progress for the field of particles characterization in steels.