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T. Rzychoń, B. Dybowski and A. Kiełbus

Abstract

The structure of Mg-9Al-2Ca-xSr alloys is composed of a-Mg grains and the Al2Ca and Al4 Sr phases in the interdendritic areas. These phases are formed as a result of eutectic reactions. Globular particles of the Al8Mn5 phase are observed within the interior of the grains. The addition of strontium to Mg-9Al-2Ca-0.4Mn alloys causes the formation of the Al4Sr phase and increase of its volume fraction with increasing strontium levels. Moreover, increase of the strontium amount causes a decrease of aluminum content in the a-Mg solid solution.

Open access

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

T. Rzychoń, J. Szala and A. Kiełbus

Microstructure, Castability, Microstructural Stability and Mechanical Properties of ZRE1 Magnesium Alloy

The influence of pouring temperature on the microstructure, fluidity and mechanical properties of ZRE1 magnesium alloy was investigated in this paper. The pouring temperature influences on the fluidity, mean area of grain plane section and mechanical properties. The dependence between pouring temperature and volume fraction of the (Mg, Zn)12RE intermetallic phase was not observed. The investigations enabled to determine the optimal pouring temperature of ZRE1 alloy. Moreover, the microstructural stability of ZRE1 alloy during long-term annealing at 150°C, 200°C and 400°C was investigated. ZRE1 magnesium alloy possesses a high microstructural stability up to 200°C, whereas at 400°C magnesium oxides and rare earth metals oxides are observed in the microstructure.

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

I. Pikos, A. Kiełbus and J. Adamiec

Abstract

The Mg-RE alloys are attractive, constructional materials, especially for aircraft and automotive industry, thanks to combination of low density, good mechanical properties, also at elevated temperature, and good castability and machinability. Present paper contains results of fatigue resistance test carried out on Elektron 21 magnesium alloy, followed by microstructural and fractographical investigation of material after test. The as-cast material has been heat treated according to two different procedures. The fatigue resistance test has been conducted with 106 cycles of uniaxial, sine wave form stress between 9 MPa and 90 MPa. Fractures of specimens, which ruptured during the test, have been investigated with scanning electron microscope. The microstructure of specimens has been investigated with light microscopy. Detrimental effect of casting defects, as inclusions and porosity, on fatigue resistance has been proved. Also the influence of heat treatment's parameters has been described.

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

B. Dybowski, J. Szymszal, Ł. Poloczek and A. Kiełbus

Due to low density and good mechanical properties, aluminium alloys are widely applied in transportation industry. Moreover, they are characterized by the specific physical properties, such as high electrical conductivity. This led to application of the hypoeutectic Al-Si-Mg alloys in the power generation industry. Proper selection of the alloys chemical composition is an important stage in achievement of the demanded properties. The following paper presents results of the research on the influence of alloys chemical composition on their properties. It has been revealed that Si and Ti addition decreases electrical conductivity of the Al-Si-Mg alloys, while Na addition increases it. The mechanical properties of the investigated alloys are decreased by both silicon and iron presence. Sodium addition increases ductility of the Al-Si-Mg alloys.

Open access

A. Dobkowska, B. Adamczyk – Cieślak, J. Mizera, K. J. Kurzydłowski and A. Kiełbus

The influence of different types of precipitation on the corrosion behavior was investigated in three aluminum-siliconmagnesium alloys. The microstructures of the alloys were studied through optical (OM) and scanning electron microscopy (SEM). The structures consisted of an α-Al solid solution matrix, Si eutectic crystals, secondary phases AlFeSi and AlMgFeSi (Chinese script), as well as Mg2Si. The corrosion behavior was examined with the use of a potentiodynamic polarization test followed by a SEM surface analysis. The results indicate that all the analyzed samples were in the passive state and AlSi10Mg was less reactive in the corrosive environment.