Metallurgy and Foundry Engineering
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ISSN 1230-2325
e-ISSN: 2300-8377
Issue Date
2014
Volume
Vol. 40
Number
No. 3
Description
Journal Volume
Metallurgy and Foundry Engineering
Vol. 40 (2014)
Projects
Pages
Articles
Structure characterization and precipitation in two Al-Mg-Si-Mn casting alloys
(2014) Link, Thomas; Bojko, Vìctorìâ; Mihalenkov, Kostântin Vìktoroviĉ
The as-cast structure of permanent mould (PM) (alloy I) and high-pressure die castings (HPDC) (alloy2) of the AlMg5Si2Mn alloy has been investigated by differential scanning calorimetry, microhardness measurements, transmission electron microscopy, and energy dispersive X-ray analysis. Inside the ?-Al grains in both alloys, curved plate-like precipitates were detected in both alloys. Examination of these precipitates revealed a number of features, such as: (1) the composition of the precipitates is very close to the stochiometric Mg2Si compound, (2) precipitates are aligned along dislocations, (3) the precipitate density is much higher for high-pressure die castings where the ?-Al matrix contains more dislocations than in permanent mould castings, (4) precipitates lie inside the ?-Al grains where they are randomly distributed. Between the Mg2Si larnellas, precipitates were not observed. Microhardness tests show that the hardness of the alloy cast into a permanent mould is lower than that of a high-pressure die casting. This observation reveals the origin of high strength in an AlMg5Si2Mn alloy subjected to HPDC.
The application of a computer technique to assess the impact of chemical composition on dispersed shrinkage microporosity of hypoeutectic cast silumins
(2014) Czekaj, Edward; Pysz, Stanisław
This article presents the possibility of decreasing dispersed shrinkage microporosity in castings of hypoeutectic alloying silumins, as a result of narrowing - within the standards or industrial specifications - the content of particular elements of the chemical composition: alloying additions and/or impurities. This relatively-simple and, at the same time, inexpensive method can often lead to a quick solution of this type of defects in castings and the improvement of their tightness. In order to orientate the chemical composition towards an optimal content, computer-aided statistical processing was conducted (using Statistica Ver. 9 software) with the application of figures directly related to shrinkage microporosity as well as indirectly related to the temperature range of crystallisation (ΔT = Tlik - Tsol). This data came from literature and MAGMASoft software for simulations of pouring and solidification processes in castings. The achieved results were verified under industrial conditions.
Methods of introducing alloying elements into liquid magnesium
(2014) Kapinos, Dawid; Augustyn, Bogusław; Szymanek, Marcin
In recent years, magnesium alloys have gained widespread popularity as construction materials. This is due to their low density, high strength properties, and advances in their production technology. Properties of magnesium alloys depend primarily on the type, quantity, and quality of elements present in their composition. It is therefore necessary to carry out research on the further optimisation of the production technology of these alloys. This article presents the results of studies carried out in order to determine the type, form, and parameters of the process of introducing selected alloying elements to magnesium in a manner which enables the manufacture of alloys with predetermined chemical composition. As part of the work, elements such as Al, Zn, Mn, Zr, Si, Cu, Ca, as well as rare earth elements (RE) were introduced into the liquid magnesium. The alloying elements were introduced into the melt at different temperatures in either a metallic form or as master alloys. While conducting studies, respective solubility graphs were plotted for the alloying elements showing the time taken for each element to dissolve to the required form at a specific temperature and concentration. The studies resulted in the development of several techniques of introducing selected alloying elements, which enabled the manufacture of various types of alloys.
Casting of Al-Si alloys in the full-mould technology - process conditions
(2014) Mocek, Jan; Zych, Jerzy; Krubnik, Łukasz
A review of various technologies using expendable casting patterns made of expanded polystyrene is given in the paper. The results of our own investigations on implementing this technology at the pilot-plant scale - for the art castings series - were presented. The results of tests of materials and moulds applied in the full-mould technology were shown. Gas evolution tendencies of expanded polystyrenes and protective coatings were estimated. Gas evolutions were described as functions of the polystyrene heating temperature. The tests of protective coatings used in this technology were performed and strength (Rm), permeability (P), and gas evolution tendency of these coatings assessed. New solutions developed by the team of researchers were applied in testing coating strength, permeability, and the gas evolution tendency of expanded polystyrene. A good correlation between the results of coating properties and the obtained casting quality was found. Coatings, which were characterised by higher strengths and better permeability, allowed us to produce castings without surface or inner faults.
Casting small-diameter ingots from multicomponent silumins
(2014) Augustyn, Bogusław; Kumor, Paweł; Kapinos, Dawid; Żelechowski, Janusz; Bigaj, Mariusz; Zamkotowicz, Zbigniew
The casting of ingots from aluminum alloys with a smali range of solidification temperatures currently poses no major technical problems. On the other hand, problems do occur when multicomponent alloys containing elements such as Cu, Zn, or Mg are cast. This applies to alloys both wrought and cast. For these alloys, the differences in temperature starting and ending the solidification process reach 160°C. The difficulties are even more pronounced when the diameter of the cast ingot is less than 100 mm. Casting small-diameter ingots requires a very careful selection of parameters, which - for ingots with a diameter of about 70 mm - usually involve very high casting rates of up to 400 mm/min. The formation of a subsurface zone in the ingot along the crystallizer working length of several centimeters is very difficult at such a high casting rate and requires the precise determination of parameters for each alloy, particularly if this is a multicomponent alloy with a wide range of solidification temperatures. To this family of alloys belong multicomponent silumins, with the special case of phosphorus-modified near-eutectic and hypereutectic systems. Below are the results of technologicaI tests as well as structure examinations of ingots cast from silumins with different ranges of solidification temperatures. Ingots of 100-mm diameters were cast in a vertical system. In this arrangement, ingots with a diameter of 70 mm were also cast, using crystallizers normally operating in a horizontal continuous casting line.