Papers by Author: Pawel Widlicki

Abstract: The aim of the work was to optimise the Hydrostatic Extrusion, HE, parameters in terms of their influence on the microstructure and certain mechanical properties of 6082 aluminium alloy. The investigations focused on the fabrication of a nano- or ultrafine-grained microstructure of the alloy. The effects of a multi-pass process were compared with those of a one-pass process producing the same cumulated true strain of 3.75. Both the multi-pass and the one-pass deformation resulted in profound grain refinement of the alloy. The microstructure contained grains with an average size of 195 nm and 239 nm, respectively. The grain refinement brought about a significant improvement in the microhardness and tensile strength of the alloy. It should be noted that the multi-pass HE produced slightly greater improvement than the single pass process.

Abstract: In this work, Al-Mg-Mn-Si alloy (5483) in the as-received and severe plastically deformed states was used. Plastic deformation was carried out by hydrostatic extrusion, and three different true strain values were applied 1.4, 2.8 and 3.8. All specimens were subjected to tensile tests and microhardness measurements. The investigated material revealed an instability during plastic deformation in the form of serration on the stress-strain curves, the so called Portevin-Le Chatelier effect It was shown that grain size reduction effected the character of the instability.

Abstract: Hydrostatic extrusion can be viewed as one of the methods of Severe Plastic Deformation, SPD, for the fabrication of ultra-fine grained alloys which causes a significant increase in the mechanical properties such as tensile strength and hardness. In the present study the microstructure of 6082 aluminium alloy after hydrostatic extrusion was investigated. Hydroextrusion was performed in three steps with accumulated true strains of 1.34, 2.73 and 3.74 respectively. Microstructural observations were carried out using SEM, TEM and light microscopy. Grain and inclusion sizes, shapes and distribution were investigated in the HE processed samples. The study has shown that the hydrostatic extrusion process results in a profound refinement of both the grain size and the inclusions in 6082 aluminium alloy.