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Morphology and Distribution of α-Al and Mn-rich Phases in Al-Si-Mn Alloys under an Electromagnetic Stirring

Mikołajczak P.

Archives of Foundry Engineering

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2023

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Vol. 23, iss. 3

74--87

EN

Convection caused by gravity and forced flow are present during casting. The effect of forced convection generated by a rotating magnetic field on the microstructure and precipitating phases in eutectic and hypoeutectic AlSiMn alloys was studied in solidification by a low cooling rate and low temperature gradient. The chemical composition of alloys was selected to allow joint growth or independent growth of occurring α-Al, α-Al15Si2Mn4 phases and Al-Si eutectics. Electromagnetic stirring caused instead of equiaxed dendrites mainly rosettes, changed the AlSi eutectic spacing, decreased the specific surface Sv and increased secondary dendrite arm spacing λ2 of α-Al, and modified the solidification time. Forced flow caused complex modification of pre-eutectic and inter-eutectic Mn-phases (Al15Si2Mn4) depending on the alloy composition. By high Mn content, in eutectic and hypoeutectic alloys, stirring caused reduction in the number density and a decrease in the overall dimension of pre-eutectic Mn-phases. Also across cylindrical sample, specific location of occurring phases by stirring was observed. No separation effect of Mn-phases by melt flow was observed. The study provided an understanding of the forced convection effect on individual precipitates and gave insight of what modifications can occur in the microstructure of castings made of technical alloys with complex composition.

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Flow Effect on Si Crystals and Mn-Phases in Hypereutectic and Eutectic Al-Si-Mn Alloys

Mikołajczak Piotr

Archives of Foundry Engineering

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2023

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Vol. 23, iss. 4

72--86

EN

During mold filling and casting solidification, melt flow caused by gravity is present. Otherwise, forced flow may be a method applied for casting properties improvement. The flow effect generated by an electromagnetic field on the growing phases and a whole microstructure in Al-Si-Mn alloys was studied by slow solidification conditions. The hypereutectic and eutectic alloys were chosen to allow independent growth or joint growth of forming: Si crystals, Mn-rich α-Al15Si2Mn4 phases and Al-Si eutectics. In eutectic alloys, where Mn-phases precipitate as first and only one till solidus temperature, flow decreased number density of pre-eutectic α-Al15Si2Mn4. In the hypereutectic alloys, where Mn-phases grow in common with Si crystals, forced convection increased the overall dimension, decreased number density of pre-eutectic Mn phases and strengthened the tendency to growth in the outside of the sample. In the alloys, where Si crystals grow as first, stirring reduce number density of Si and moved them into thin layer outside cylindrical sample. Also by joint growth of Si crystals and Mn-phases, in hypereutectic Mn/Si alloy, flow moved Si crystals outside, reduced number density and increased the dimension of crystals. Stirring changed also AlSi eutectic spacing, specific surface Sv of α-Al and secondary dendrite arm spacing λ2. The results gave insight of what transformation under stirring take place in simple Al-Si-Mn alloys, and helps to understand what modifications in technical alloys may occur, that finally lead to changes in castings microstructure and properties. The possibility to control dimension, number density and position of Mn-phases and Si crystals is completely new and may help by metallurgical processes, continuous casting of billets and in the production of Si for the solar photovoltaic industry.

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Wpływ procesu aluminiowania na mikrostrukturę nadstopu niklu Inconel 713C

Zagórska M., Sitek R., Dobkowski K., Kurzydłowski K. J.

Inżynieria Materiałowa

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2015

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Vol. 36, nr 3

120--123

PL

Warstwy ochronne na bazie międzymetalicznej fazy NiAl są stosowane do poprawy odporności na utlenianie wysokotemperaturowe odpowiedzialnych elementów turbin silników lotniczych.W pracy dyfuzyjną warstwę Ni0.58Al0.42 modyfikowaną cyrkonem wytworzono metodą CVD z par AlCl3 + ZrCl3 w atmosferze wodoru jako gazu nośnego, w temperaturze 1040°C przez 3 h, pod ciśnieniem 150 hPa na podłożu nadstopu niklu IN 713C. Wykonano badania mikrostruktury warstwy oraz jej składu chemicznego i fazowego. Zbadano także wpływ procesu aluminiowania na mikrostrukturę podłoża — nadstopu niklu IN713C. Stwierdzono, że wytworzone warstwy wykazują ciągłość na całej powierzchni próbek, stabilność składu chemicznego i fazowego oraz nie wpływają na mikrostrukturę stopu.

EN

Protective layers based on NiAl intermetallic phases are commonly used in improving high-temperature oxidation resistance of responsible aircraft engines turbine components. In this work zirconia modified diffusion layer Ni0.58Al0.42 was manufactured on nickel-based superalloy IN 713C by CVD method with the presence of AlCl3 + ZrCl3, in an atmosphere of hydrogen as a carrier gas, at a temperature of 1040°C, during 3 h and at a pressure of 150 hPa. Microstructure, chemical and phase composition of layers were studied. The influence of aluminizing process on the microstructure of substrate was also examined. It was found that obtained layers are characterized by stability of chemical and phase composition and does not change the microstructure of the substrate.