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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
Despite the tendency of the current industry, especially the automotive industry, it is to use modern, light and super-strong materials based on Al or HSLA steels, the application of classic materials such as cast iron still makes sense, especially concerning price and excellent castability. The article presents one of the possible ways of using the ultrasonic non-destructive method in quality control and simpli-fication of the identification of the type of cast iron concerning the change of parameters of ultrasound propagation in materials. The main criteria for assessing the quality and determining the type of graphite cast iron were considered to be the rate of propagation of ultrasound - cL and the value of attenuation , which vary depending on the shape of the graphite and matrix. Graphitic cast irons with different graphite shapes (lamellar, vermicular, and globular shapes) and a matrix with different ferrite/perlite ratios were used as experimental material. Along with the ultrasonic tests, a metallographic analysis was also performed to quantify the microstructure of cast irons.
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
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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