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  • Author: P. Mikołajczak x
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P. Mikołajczak and L. Ratke

Abstract

Iron exists as a common impurity element in AlSi foundry alloys. The main consequence of the presence or adding of iron to AlSi alloys is the formation Fe-rich intermetallics with especially deleterious β-Al5FeSi. This work aims to identify the role of fluid flow on the microstructure and intermetallics in Al-9 wt.% Si-0.2/0.5/1.0 wt.% Fe alloys directionally solidified under defined thermal and fluid flow conditions and extensively uses 3D x-ray tomography to get a better insight into their morphology and formation. The results have revealed the growth of larger and more dense β-Al5FeSi intermetallics in the specimen centre as an effect of forced flow. The reconstructions confirmed that the course of number density at the specimen cross section increases from the specimen edge to its centre.

Open access

P. Mikołajczak and L. Ratke

Abstract

Directional solidification technique is an important research instrument to study solidification of metals and alloys. In the paper the model [6,7,8] of directional solidification in special Artemis-3 facility was presented. The current work aimed to propose the ease and efficient way in calibrating the facility. The introduced M coefficient allowed effective calibration and implementation of defined thermal conditions. The specimens of AlSi alloys with Fe-rich intermetallics and especially deleterious β-Al5FeSi were processed by controlled solidification velocity, temperature gradient and cooling rate.

Open access

P. Mikołajczak and L. Ratke

Abstract

Solidification of AlSiFe alloys was studied using a directional solidification facility and the CALPHAD technique was applied to calculate phase diagrams and to predict occurring phases. The specimens solidified by electromagnetic stirring showed segregation across, and the measured chemical compositions were transferred into phase diagrams. The ternary phase diagrams presented different solidification paths caused by segregation in each selected specimen. The property diagrams showed modification in the sequence and precipitation temperature of the phases. It is proposed in the study to use thermodynamic calculations with Thermo-Calc which enables us to visualize the mushy zone in directional solidification. 2D maps based on property diagrams show a mushy zone with a liquid channel in the AlSi7Fe1.0 specimen center, where significant mass fraction (33%) of β-Al5FeSi phases may precipitate before α-Al dendrites form. Otherwise liquid channel occurred almost empty of β in AlSi7Fe0.5 specimen and completely without β in AlSi9Fe0.2. The property diagrams revealed also possible formation of α-Al8Fe2Si phases.

Open access

P. Mikołajczak and L. Ratke

Abstract

Iron is the most common and detrimental impurity in casting alloys and has been associated with many defects. The main consequence of the presence or adding of iron to AlSi alloys is the formation Fe-rich intermetallics with especially deleterious β-Al5FeSi. β-Al5FeSi phases are most often called needles on 2D micro sections, whilst platelets in 3D geometry. The x-ray tomography results have demonstrated Ferich phases with shapes different from simple forms such as needles or platelets and presented bent and branched phases. β grown as complicated structure of bent and branched intermetallics can decrease feeding ability, strengthen pores nucleation and eutectic colonies nucleation leading to lower permeability of mushy zone and porosity in the castings.

Open access

W. Buchwald, P.Ł. Mikołajczak, A. Krajewska-Patan, M. Dreger, M. Górska-Paukszta, M. Szulc, P. Polcyn, A. Pioruńska-Mikołajczak, S. Mielcarek, B. Czerny, P.M. Mrozikiewicz and T. Bobkiewicz-Kozłowska

Abstract

The present study was carried out to investigate the protective effects of roots of Salvia miltiorrhiza Bunge on hypobaric hypoxia. Two extracts of S. miltiorrhiza (extract 1: ethanol : water - 50 : 50; extract 2: 96% ethanol) were used. The experiments were performed after 7 consecutive days of administration of the extracts (200 mg/kg b.w., intragastrically) to male Wistar rats. Next, after placing animals for 60 min in the controlled acute hypobaric hypoxia (500 mm Hg) the systolic arterial blood pressure (SAP) in conscious rats, bioelectric heart activity in unconscious rats and analysis of oxidative stress parameters in the blood of rats: malonyldialdehyde (MDA) and lipid peroxidase (LPO) concentration, activity of superoxide dismutase (SOD) or glutathione peroxidase (GPX) were assayed. It was found out that the extract 1 augmented the lowering of SAP shown in hypoxia affected control rats. On the contrary the extract 2 reversed SAP to values obtained in control animals. Moreover, both extracts led to the normalization of hypoxia-induced tachycardia and levels of MDA, LPO and SOD. It seems that the above-mentioned effects are coupled with different active compounds content in the extracts, however more studies are needed to confirm this hypothesis.

Open access

J. Mikołajczak, S. Borowski, J. Marć-Pieńkowska, G. Odrowąż-Sypniewska, Z. Bernacki, J. Siódmiak and P. Szterk

Abstract

Wind farms produce electricity without causing air pollution and environmental degradation. Unfortunately, wind turbines are a source of infrasound, which may cause a number of physiological effects, such as an increase in cortisol and catecholamine secretion. The impact of infrasound noise, emitted by wind turbines, on the health of geese and other farm animals has not previously been evaluated. Therefore, the aim of this study was to determine the effect of noise, generated by wind turbines, on the stress parameters (cortisol) and the weight gain of geese kept in surrounding areas. The study consisted of 40 individuals of 5- week- old domestic geese Anser anser f domestica, divided into 2 equal groups. The first experimental gaggle (I) remained within 50 m from turbine and the second one (II) within 500 m. During the 12 weeks of the study, noise measurements were also taken. Weight gain and the concentration of cortisol in blood were assessed and significant differences in both cases were found. Geese from gaggle I gained less weight and had a higher concentration of cortisol in blood, compared to individuals from gaggle II. Lower activity and some disturbing changes in behavior of animals from group I were noted. Results of the study suggest a negative effect of the immediate vicinity of a wind turbine on the stress parameters of geese and their productivity.