Majchrowska, Magdalena
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inżynieria materiałowa
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Item type:Article, Access status: Open Access , Effect of particle size of a powder upon the properties and microstructure of boron-modified Fe-Ni-Mo-Cu sinters(AGH University Press, 2023) Karwan-Baczewska, Joanna; Perek-Nowak, Małgorzata; Majchrowska, Magdalena; Rosso, MarioThe article discusses the effect of different particle fractions of prealloyed iron powder on the microstructure, density and hardness of sintered material. Each particle fraction (apart from 160-200 μm, which is a trace fraction) was modified with boron, its contents being, respectively, 0.2 wt.%, 0.4 wt.% and 0.6 wt.%. Next, the powder mixtures were pressed under a pressure of 600 MPa, and the final compacts were subject to sintering at 1200°C for 60 min in a hydrogen atmosphere. It was observed that the higher values of density and hardness were found in samples made from finer fractions of powder. A higher homogeneity of the microstructure and the highest degree of compactness was obtained in sinters from powder of 40-56 μm particle size, with 0.4 wt.% B. Due to the use of small particle fractions of prealloyed powder, a higher degree of compactness in sinters was obtained with lower boron content. Also indicated was which particle fraction of Fe-Ni-Mo-Cu powder should be applied to obtain density in sinters with boron addition equal to almost 100% of the relative density of the analyzed alloy. The presented studies have both scientific and technological aspects.Item type:Article, Access status: Open Access , Research on mechanical and electrical properties of Cu-Ag alloys designed for the construction of high magnetic field generators(AGH University of Science and Technology Press, 2021) Kawecki, Artur; Sieja-Smaga, Eliza; Korzeń, Kinga; Majchrowska, Magdalena; Noga, PiotrThe individual sections, wiring and construction of electromagnet windings responsible for strong magnetic field impulses may be one application for hypoeutectic Cu-Ag alloys. High electrical properties and mechanical properties (tensile strength, yield strength, impact strength) as well as high heat, fatigue and rheological resistance are required for these kinds of applications due to the unique nature of such operations (strong vibrations of high frequency and amplitude resulting from Lorenz forces and the possibility of significant and rapid heating from Jule's heat). The limited solubility of copper and silver in the solid state enables the effective modification of the alloys' microstructure through heat treatment and further shaping of their high mechanical and electrical properties via cold plastic working. The article presents the manufacturing of Cu-Ag alloys with the weight percent of Ag between 3 and 7 using the continuous casting process along with research on the physicochemical, mechanical and electrical properties of the obtained casts. The research on the amount of plastic deformation and its influence on the wire drawing process and the mechanical and electrical properties of the wires is also discussed. The temperature coefficients of resistance were defined in order to determine the temperature influence on the electrical resistance changes dynamics. The microstructural analysis was carried out in the as-cast state. The preliminary research conducted indicates that the obtained Cu-Ag alloys in the as-cast state exhibit a set of high mechanical and electrical properties. The prospective next stage of research includes the selection of favourable heat treatment parameters which would provide optimally modified microstructure of the alloys, as well as determining the deformation coefficients allowing for further increases in the mechanical and electrical properties.