We investigate micro-structural changes in powder metallurgical samples of carbonyl-iron and stainless steel by different methods: X-ray diffraction and positron annihilation spectroscopy. Positron annihilation gives information about dislocation densities and porosity in PM-samples. The sample are sintered to certain stages and then rapidly cooled to freeze-in this stage for the ex-situ investigations.
Dimensional changes and possible warping are recorded for samples up to 40mm in diameter by our thermo-optical measurement device with atmospheric control (TOM-AC). This contact-less methods allows to follow dimensional changes (accuracy of 0.5 microns) of samples up to 40mm in diameter.
During the sintering process we apply several load levels to investigate the influence of effects caused in processes employing constrained sintering. Additionally, the sintering atmosphere has been varied during the heat treatment (pure inert gases (Ar, N) and Ar-/N-Hydrogen mixtures).