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B. Dybowski, A. Kiełbus and R. Jarosz

Abstract

We investigated the impact of the applied cooling and feeding method on the microstructure and metallurgical quality of castings made from WE43 magnesium alloy. Six identical plates with dimensions of 100x50x20 mm were sand cast for use as samples. Each casting was fed and cooled in a different way. The solid solution grain size was evaluated quantitatively using the Met-Ilo software program, and casting defects were observed using a scanning electron microscope Hitachi S3400N. The finest solid solution grain was observed in the castings with only the coolers applied. Non-metallic inclusions were observed in each plate. The smallest shrinkage porosity was observed in the castings with feeders applied.

Open access

A. Kiełbus, M. Stopyra and R. Jarosz

The paper present the influence of modifying process on chemical composition, microstructure, and selected properties of Mg alloys. Two sand-casting creep-resistant alloys, Elektron 21 and WE43, were analyzed in various forms: without modifiers, with the amount of modifier suggested by the producer, and with this amount increased by 50% and 100%. The volume fraction of eutectic areas, tensile strength, and yield strength were measured and the fluidity and linear contraction were analyzed. The research shows that, in contrast to what is widely assumed to be a positive influence of rare-earth elements on Mg alloys properties, a large increase in the amount of modifiers does not always lead to an improvement in the alloy properties. However, the results are tentative because they may have been influenced by the melting technology used, which can be improved. Rare-earth elements tend to react with fluxes, which could lead to a decrease in mechanical properties and fluidity. More research is planned wherein the alloys are melted under a protective atmosphere.

Open access

B. Dybowski, A. Kiełbus and R. Jarosz

Abstract

Magnesium alloys due to their low density and high strength-to-weight ratio are promising material for the automotive and aerospace industries. Many elements made from magnesium alloys are produced by means of sand casting. It is essential to investigate impact of the applied mould components on the microstructure and the quality of the castings. For the research, six identical, 100x50x20mm plates has been sand cast from the Elektron 21 magnesium casting alloy. Each casting was fed and cooled in a different way: one, surrounded by mould sand, two with cast iron chills 20mm and 40mm thick applied, another two with the same chills as well as feeders applied and one with only the feeder applied. Solid solution grain size and eutectics volume fraction were evaluated quantitatively in Met-Ilo program, casting defects were observed on the scanning electron microscope Hitachi S3400N. The finest solid solution grain was observed in the castings with only the chills applied. Non metallic inclusions were observed in each plate. The smallest shrinkage porosity was observed in the castings with the feeders applied.

Open access

Ł. Poloczek, B. Dybowski, K. Rodak, R. Jarosz and A. Kiełbus

Aluminium alloys are characterized by a low density, acceptable mechanical properties and good technological properties. This unique connection of features made aluminium alloys perfect structural material for the transportation industry. Also, due to their good electrical conductivity they also found application in energy production industry. High mechanical properties and electrical conductivity of the Al-Si alloys with Mg addition may be achieved by heat treatment. However, the highest mechanical properties are achieved in the early stages of age hardening - due to precipitation of coherent phases, while high electrical conductivity may be achieved only by prolonged aging, during precipitation of semi-coherent or fully noncoherent, coarse phases. Carefully heat treated AlSi7Mg alloy may exhibit both fairly high electrical conductivity and slightly increased mechanical properties. The following article present results of the research of influence of heat treatment on the properties and microstructure of sand cast AlSi7Mg alloy. Microstructure observations were performed using light microscopy, scanning electron and scanning-transmission electron microscopy. Hardness and electrical conductivity of the AlSi7Mg alloy were investigated both in as-cast condition and after heat treatment. Maximum hardness of the alloy is achieved after solutioning at 540°C for 8h, followed by 72h of aging at 150°C, while maximal electrical conductivity after solutioning at 540°C for 48h, followed by 96h of aging at 180°C. Increase of the electrical conductivity is attributed to increasing distance between Si crystals and precipitation of semi coherent phases.

Open access

G. Jarosz, B. Kościelska and R. Signerski

Abstract

This work presents experimental studies of a planar diode made of the layers of indium tin oxide, titanium dioxide, palladium phthalocyanine and gold. The current rectification ratio was 105 at 1.5 V. The analysis of the electrical properties of the system was based on small signal complex capacitance spectra measured in the frequency range of 25 Hz — 1 MHz at different values of bias. No depletion region at the TiO2/PdPc interface was observed. Forward bias specifically affected both parts of the complex capacitance and the observed effect probably resulted from the rearrangement of charge carriers injected into the organic layer.