Papers by Author: Tomasz Czeppe

Abstract: Orientation mapping in transmission electron microscope was successfully applied to study microstructural changes at the initial stage of recrystallization in the aluminum alloy with a bimodal second-phase particle distribution. The alloy samples were reversibly cold rolled resulting in the formation of laminar structure with zones of localized strain around large second-phase particles. Orientation mapping and in-situ investigations carry information about the processes which are active in the deformation zones during annealing.

Abstract: In the present work we report our studies of temperature dependence of magnetization and structure analysis of Lu2Fe17 samples. The samples revealed various, coarse grained, submicrocrystalline, and nanocrystalline microstructures. It was found that in nanocrystalline state the Lu2Fe17 compound has a higher coercive force, retains phase composition and does not disintegrate during heating. The curves of the temperature dependence of magnetization were recorded for all investigated structural states and indicated that nanocrysatlline sample had a higher Curie point.

Abstract: This work is focused on the effect of the combination of natural aging and severe plastic deformation (SPD) produced by Equal-Channel Angular Pressing (ECAP) on the microstructure and strength of supersaturated AlZnMg alloys. Following a solution heat-treatment and quenching into water at room temperature, samples were naturally aged for different time periods and then processed by ECAP. The microstructure and mechanical properties of these samples are described and discussed. This investigation leads to proposing an interesting application of ECAP for supersaturated alloys. Using the shear bands created by ECAP in only one pass and applying appropriate subsequent aging treatments, composite-like microstructures can be achieved in conventional age-hardenanble Al alloys.

Abstract: Influence of the Ga alloying on the crystal structure and parameters of the martensitic transformation are presented. X-ray diffraction has shown the multiphase composition of the samples (β (B2)- phase, γ′ (L12)-phase, (L10)-martensitic phase, Ni5Al3-phase). Metallographic investigations have demonstrated the coarse grain of B2 phase with non-regular needles of Ni3Al and typical martensitic structure. Ga did not suppress the martensitic transformation in NiAlGa alloys. The Ni to Al ratio and quantity of Ga determine the parameters of martensitic transformation.