Abstract. Treatment of metal alloys is one of the ways to affect the quality and properties of the material. This also applies to aluminum alloys. Nowadays so-called silumins are often used One of them is also the alloy AlSi7Mg0.3, which is used for production of casting parts. The article describes one of the experiments in the area of modification of Al-Si alloys, realized at the Faculty of Mechanical Engineering of Jan Evangelista Purkyně Univesity in Ústí nad Labem, when the influence of calcium (Ca) on alloy AlSi7Mg0.3 was experimentally studied. Calcium is one of the elements, which is possible to be used for changing of aluminium alloys properties, but as it is possible to read in literature, the view on its influence differs, whether it is bad or good. The alloy was modified with various amounts of calcium. Experimental quantities of calcium were 0.05, 0.2, 0.3 and 0.4 percent by weight. Experimental alloys were made from individual components. The final microstructure of each alloy and their hardness were analysed. For this the confocal laser scanning microscope LEXT OLS 3100 and hardness tester Ernst AT 250X were used, which are available at the FME. Experimental samples were machined, too and tool wear of using cutting inserts was analysed, and the shape of the chip was measured. It was realized with the light microscope Olympus SZX 10. The presented experiments and measurements are part of the extensive research undertaken at the Faculty of Mechanical Engineering at Jan Evangelista Purkyně University in Ústí nad Labem.Keywords: aluminium, modification, alloy, machining.
IntroductionFor various reasons, as it is generally known, alloys are adjusted (alloyed, inoculated and modified). Of course, this also applies to aluminum alloys. These reasons are, eg., to improve the physical and technological properties. At the Faculty of Mechanical Engineering in this context various experiments were implemented just with aluminum alloys. One of them is research in the effect of different amounts of selected elements to certain aluminum alloys. One of the investigated elements is calcium (Ca), which can be used as the modifying element, in particular of Al-Si alloys. This improves the morphology of silicon in the alloy. It also improves the castability of aluminum alloys. But also it has negative effects, e.g., deterioration of the homogeneity of the resulting microstructure and is therefore considered as a harmful element. As the research shows, the important thing is the amount of it [1][2][3][4].Modification of aluminum alloys is a process, by which the melt is deliberately modified by various elements in order to influence the mechanism of eutectic solidification. Modification changes the morphology and size of crystals of silicon (in the case of Silumin), causing a significant increase in the mechanical properties compared to unmodified alloys. Large size silicon of crystals has lower strength properties of Al-Si alloys. Strength and plastic properties of the modified alloys are therefore higher in compariso...