Among metals, aluminium is one of most common material used in various applications, almost always with certain alloying elements (Cu, Mg, Si, Mn, Zn, Fe, etc.) to get as close as possible to desired properties of material. Adding silicon for example, improves castability and increases resistance to wear. Manganese (up to 0.6 mass %) prevents formation of an undesirable β-Al5FeSi phase, which is needle-shaped that causes notch effect and poorer mechanical and corrosion properties. In order to reduce the eutectic β-Si, the Na or Sr modifiers are usually added. Phosphorus is added to reduce the size of primary β-Si. Size of crystal grain α-Al is influenced by the addition of the Al-Ti-B grain refiner. The addition of Mg (0.4 to 0.6 mass %) and Cu (0.7 to 2.5 mass %) in alloys of Al-Si allow the percipitation hardening. Zinc is added to get high ductility and good mechanical properties and it also reacts with copper and magnesium which then forms alloys with a high solidus temperature.
The purpose of the diploma work was to analyse the effect of addition of molybdenum and zirconium on the process of solidification and the formation of the cooling curve of the alloy Silafont-36 (AlSi10MnMg). We used the Silafont-36 alloy and two master alloys AlMo5 and AlZr10. We made six experimental samples with various concentrations and combinations of zirconium and molybdenum. After a chemical analysis, we used ThermoCalc program to calculate the course of equilibrium solidification and equilibrium phase diagram. Next we recorded the cooling curve and by using the derivative of the cooling curve in the Origon 9.0 program we determined the transformation temperatures of phases during solidification. Based on the results of differential scanning calorimetry (DSC) and thermodynamic equilibrium calculation we characterized obtained temperatures of different solidification phases. In that way we were able to determine influence of Zr and Mo on the solidification of Silafont-36 alloy.
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