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Abstract

Secondary or multiple remelted alloys are common materials used in foundries. For secondary (recycled) Al-Si-Cu alloys, the major problem is the increased iron presence. Iron is the most common impurity and with presence of other elements in alloy creates the intermetallic compounds, which may negatively affect the structure. The paper deals with effect of multiple remelting on the microstructure of the AlS9iCu3 alloy with increased iron content to about 1.4 wt. %. The evaluation of the microstructure is focused on the morphology of iron-base intermetallic phases in caste state, after the heat treatment (T5) and after natural aging. The occurrence of the sludge phases was also observed. From the obtained results can be concluded that the multiple remelting leads to change of chemical composition, changes in the final microstructure and also increases sludge phases formation. The use of heat treatment T5 led to a positive change of microstructure, while the effect of natural aging is beneficial only to the 3rd remelting.
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Abstract

The paper deals with influence of multiple remelting on AlSi9Cu3 alloy with higher iron content on chosen mechanical properties. Multiple remelting may in various ways influence mechanical, foundry properties, gas saturation, shrinkage cavity, fluidity etc. of alloy. Higher presence of iron in Al-Si cast alloys is common problem mainly in secondary (recycled) aluminium alloys. In Al-Si alloy the iron is the most common impurity and with presence of other elements in alloy creates the intermetallic compounds, which decreases mechanical properties. Iron in the used alloy was increased to about 1.4 wt. %, so that the influence of increased iron content can be investigated. In the paper, the effect of multiple remelting is evaluated with respect to the resulting mechanical properties in cast state, after the heat treatment (T5) and after natural aging. From the obtained results it can be concluded that the multiple remelting leads to change of chemical composition and affect the mechanical properties.
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Abstract

A comprehensive understanding of melt quality is of paramount importance for the control and prediction of actual casting characteristics. Among many phenomenon that occur during the solidification of castings, there are four that control structure and consequently mechanical properties: chemical composition, liquid metal treatment, cooling rate and temperature gradient. The cooling rate and alloy composition are most important among them. This paper investigates the effect of the major alloying elements (silicon and copper) of AlSi-Cu alloys on the size of secondary dendrite arm spacing. It has been shown that both alloying elements have reasonable influence on the refinement of this solidification parameter
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Abstract

The research focused on the influence of the solution temperature on the structure of precipitation hardening multi-component hypoeutectic aluminium alloys. The AlSi8Cu3 and AlSi6Cu4 alloys were used in the study and were subjected to a thermal-derivative analysis. The chemical composition and crystallization of phases and eutectics shift the characteristic points and the corresponding temperatures to other values, which affect to, for instance, the solution temperature. The alloys were supersaturated at 475°C (according to the determined temperature (TSol) and 505°C for 1.5 hours. Aging was performed at 180°C for 5 hours. The Rockwell hardness measurement, metallographic analysis of alloys by means of light microscopy as well as chemical and phase analysis using scanning electron microscopy and X-ray crystallography were carried out on alloys. The use of computer image analysis enabled the determination of the amount of the current Al2Cu phase in the alloys before and after heat treatment.
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