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EN
The aim of this paper was to analyze the impact of varying zirconium addition on selected properties of AlSi5Cu2Mg alloy. The results of this research showed that zirconium addition in the range of 0.05 to 0.20 wt. % caused a decrease in ultimate tensile strength and yield strength of the experimental alloys after T7 heat treatment, probably due to the formation of primary Al3Zr intermetallic phases. These phases were observed as an individual plates or as a formation of two crossed plate-like phases. Potentiodynamic polarization tests in 3.5% NaCl solution revealed that addition of Zr had a positive effect on thermodynamic corrosion stability of the AlSi5Cu2Mg alloy due to shift of the corrosion potential to a more positive values for all as-cast samples. Addition of Zr in the as-cast alloys improved corrosion kinetics by lowering of corrosion current density.
EN
Due to the high demand for secondary alloys in the automotive and aerospace industry, this work investigates the effect of higher iron content on the quality of AlSi7Mg0.6 sand castings. Secondary-recycled Al-Si alloys contain an increased amount of impurities due to their remelting of scrap metal. One of the most unwanted impurities found in these alloys is iron. Iron leads to the formation of various Fe-rich intermetallic phases, whose morphology influences the mechanical properties even at low Fe content. It also promotes the formation of casting defects, such as porosity and shrinkage. The formation of porosity in secondary Al-alloys is another major aspect that can affect the final properties of castings. Since these materials are mainly used to produce castings for the automotive industry, such as engine blocks, cylinder heads, and so on, it is necessary to produce castings without any defects. Therefore, the quality of AlSi7Mg0.6 sand casting is investigated at lower iron content (0.128% wt. Fe) and compared to the higher iron content (0.429% wt. Fe), whereby a correlation between iron content and porosity is monitored.
EN
Designers have a major interest about fatigue properties of materials used in transport industry. Each component in transport works under alternating stress. From this point of view the fatigue properties are important for single parts lifetime resulting into safety of whole components as cars and airplanes what leads to safety on the roads or air and have influence on human life as well. Therefore this paper deals with fatigue properties of wrought Inconel alloy IN 718 and aluminum cast alloy AlSi9Cu3. Both materials were put on fatigue push – pull test, but Ni – based IN 718 alloy at frequency of loading around 20 000 kHz (High Frequency High Cycles Fatigue) and aluminum alloy AlSi9Cu3 at frequency of loading around 80 Hz (Low Frequency High Cycles Fatigue). These parameters were chosen with respect of usage such materials for production of components used in transport industry applications. Results after fatigue tests are presented as Wohler curve. For prediction of source of fracture the SEM fractography analysis of fatigue fracture surfaces was made.
EN
This paperwork is focused on the quality of AlSi6Cu4 casting with different wall thicknesses cast into the metal mold. Investigated are structural changes (the morphology, size, and distribution of structural components). The quantitative analysis is used to numerically evaluate the size and area fraction of structural parameters (α-phase, eutectic Si, intermetallic phases) between delivered experimental material and cast with different wall thicknesses. Additionally, the Brinell hardness is performed to obtain the mechanical property benefits of the thin-walled alloys. This research leads to the conclusion, that the AlSi6Cu4 alloy from metal mold has finer structural components, especially in small wall thicknesses, and thus has better mechanical properties (Brinell hardness). These secondary Al-castings have a high potential for use in the automotive industry, due to the thin thicknesses and thus lightweight of the construction.
EN
Self-hardening aluminium alloys represent a new and interesting group of aluminium alloys. They have the advantage that they do not need to be heat treated, which is an important advantage that contributes to a significant reduction in production costs of some components and in the amount of energy used. The present paper deals with the possibility to replace the most used heat treatable AlSi7Mg0.3 cast alloys with a self-hardened AlZn10Si8Mg cast alloy. In this study, microstructural characterization of tensile and fatigue-tested samples has been performed to reveal if this replacement is possible. The results of fatigue tests show that AlSi7Mg0.3 alloy after T6 heat treatment and self-hardened AlZn10Si8Mg has comparable values of fatigue properties. The self-hardening alloy has slightly lower strength, ductility, and hardness.
EN
Colour Metallography is a set of light metallographic microscopy methodologies that utilize phase colour contrast as a source of new structure information compared to conventional techniques. In many cases, colour contrast can be induced where no identifiable phase contrast is obtained by conventional techniques. With the help of colour contrast, we gain new information on the structure of Al-Si alloys, especially intermetallic phases, in which the benefits of its use in casting quality control are of benefit. Blue-yellow contrast is definitely more pronounced than dark grey or light grey contrast. There is no substantial reproducible colour reproduction, since it is irrelevant whether the two phases are distinguished by blue-yellow or green-ocher contrast. When using the colour contrast, the structural components differ not only according to their microscopic appearance, but also based on the knowledge of the chemical composition of alloys, interactions between structural components, knowledge of the possible influence of Al-alloys structure (e.g. refining, modifications, heat treatment). Colour contrast in quality control of Al-Si alloys was applied to AlSiMg cast alloy (AlSi7Mg0.3; AlSi7MgTi; AlSi10MgMn; etc.).
EN
The effect of possible modification and refining effect of Al-Cu-P-based pre-alloy combined with Fe on the microstructure and the silicon morphology change in hypereutectic Al-Si cast alloy was studied. The samples in the as-cast state were observed by optical and scanning electron microscopy with energy-dispersive X-ray spectroscopy. The 3D morphology of both primary and eutectic silicon was observed by using colour and deep etching in detail. The results showed that the AlCu19P1.4 pre-alloy (1.07 wt.%) combined with the addition of Fe (0.02 wt.%) has a significant effect on the change of the amount, size and morphology of primary Si. This is significantly refined and changes the shape from a coarse irregular star-shaped, polyhedral, or plate-like shape to a fine polyhedral shape. The average size of the primary Si is reduced by about of 78 % from 135 μm to 28 μm and the number of primary Si particles increased from 7.4 to 237. No change in the morphology of the eutectic Si was observed; a refinement of the structure from a coarse needle/plate-like to a fine plate-like structure was seen. The depth etching method using HCl was very effective in the study of the 3D silicon morphology observed, which could be observed in detail without the presence of artefacts.
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