Key Engineering Materials Vol. 635

Abstract: Molten aluminium alloy is so active that it an easily chemically react with O₂ and H₂O to form Al₂O₃ inclusions and H during melting practice. However, some other inclusions form by process. Under turbulent flow conditions, the inclusions are distributed unevenly in molten aluminium alloy. They may associate with crack or by the location of crack initiation in solidified casting. Castings containing these inclusions will probably exhibit poor ductility or toughness. Therefore, the purification of the molten aluminium alloy is one of the most important processes for improving the quality of Al-products. The inclusions in molten secondary AlSi7Mg0.3 cast alloy (without refining or modification; grain refined with 55 ppm AlTi5B1 and modified with 20, 40 and 60 ppm AlSr10) were removed using depth filtration by ceramic foam and pressed filter. The results showed that the mechanical properties through filtration changes. Ductility and UTS of the filtered tensile specimens increases. The better mechanical properties were measured by the using of pressed ceramic filter. Highest UTS and ductility was observed for samples modified with 40 ppm of Sr. Filtration with ceramic filters have very significant influence on the porosity decreasing; in the process the better effect has a pressed filter. In samples modified with 60 ppm of Sr were observed effect of over modification (mechanical properties decreased; porosity increased).

Abstract: The contribution deals with comparison of microstructure, mechanical properties and fatigue properties of synthetic nodular cast irons with a different ratio of steel scrap in a charge. Chemical composition of individual melts was regulated alternatively by ferrosilicon (FeSi) and carburizer or metallurgical silicon carbide (SiC). The paper shows positive influence of SiC additive on the microstructure, mechanical properties as well as fatigue properties of nodular cast iron. The additive of metallurgical silicon carbide in analysed specimens increases the content of ferrite in the matrix, decreases the size of graphite and increases the average count of graphitic nodules per unit of area. Consequently, the mechanical and fatigue properties of nodular cast iron are improved.

Abstract: The Inconel’s alloy IN 718 has been developed by International Nickel Company in early 50-ties of 20^th century. It is high-strength; corrosion-resistant nickel chromium material used at temperature range from-250°C up to 705°C. In this study, the high cycle fatigue (HCF) and very high cycle fatigue (VHCF) properties of IN718 superalloy with given chemical composition were investigated under push-pull high frequency fatigue test at room temperature. A S – N curve was obtained after testing. With the help of scanning electron microscope (SEM), fractography analyses were performed to disclose the fracture features of specimens in different life ranges.

Abstract: The Al-Si cast alloy mechanical properties and microstructure depends on the chemical composition; melt treatment conditions, solidification rate, casting process and the applied thermal treatment. Modification can be achieved by several methods as faster solidification, mould vibration, and melt inoculation by using chosen elements like Sr, Na, Sb, etc. Present work is focused on study of the effect of Sb-modification (with AlSb10 from 0 up to 300 ppm) on the structure and mechanical properties in AlSi7Mg0.3 cast alloy. AlSi7Mg0.3 alloy can be used for high temperature casting (e.g. engine, pistons) therefore is necessary to determine the properties at higher temperature. The mechanical properties were evaluated at room (21 °C) and 260 °C. The results show that the modification of experimental material is important. Experimental alloy has by optimal modification (50 ppm Sb) UTS at 260 °C above 100 MPa.

Abstract: The effect of severe plastic deformation by ECAP process on the microstructures and mechanical properties of the aluminium alloy EN AW 6082 produced by cold extrusion is investigated. In both states were evaluated the structural changes by light microscopy, the analysis particles in structures, by X-ray diffraction (XRD) in transmission mode by synchrotron radiation and mechanical properties. Severe plastic deformation leads to strengthening of investigated EN AW 6082 alloy but on the other hand the plasticity of ECAP-ed alloy decreases.

Abstract: Liquid storage tanks are used to store of liquids. During earthquake activity the liquid exerts impulsive and convective pressures (sloshing) on the walls and bottom of tank. In the present paper, experimental and analytical study is taken up to obtain sloshing frequency of liquid contained in rectangular calculating of circular frequencies fluid in rectangular container. Analytical results of first natural frequency are compared with experiment.

Abstract: The goal of this paper is to calculate of thermal physical and environmental parameters of lower structure to support decision at the design phase of the project. The solutions are towards reduced embodied environmental impacts and improved energy performance. This study uses life cycle analysis in system boundary from Cradle to Gate and focuses on environmental indicators such as embodied energy and emissions of CO_2eq. and SO_2eq. The selection and combination of materials influence amount of energy consumption and associated production of emissions during building operation phase.

Abstract: Safety and traffic flow of production facilities also depends upon the reliability of technical security equipment. Gearing in the transmission mechanisms must satisfy the conditions of strength calculation. This calculation consists of checking of the gear teeth on bend and contact. From the stress of gears is show that the basic requirements of the material are high hardness of works surfaces and bending strength. Steels best meet these conditions. Used steel with surface hardness up to 350 HBW, or heat treated steel with hardness of 500-650 HBW. The advantage of these materials is the high value of the contact pressure in the tough centre core of the tooth. As a final heat treatment are used surface hardening, cementation and hardening, nitridation and carbo-nitridation. Good properties of heat-treated steels are at the correct thickness of the heat-treated layer of the tooth. This paper considers the appropriate choice of parameters to obtain the desired level of safety of gears in a gearbox to drive the conveyor in the metallurgical industry under increased load.

Abstract: The contribution deals with joining of materials and creating of bushes from aluminum materials, with using of new joining technologies by thermal drilling, it means by Flowdrill method. This method is using at joining of materials such as sheets, pipes, hollow profiles, where the thickness of material does not allow to make the drilling with enough number of threads. Also we can compare this thermal drilling technology with production of smooth cylindrical and conical bushings by forming technologies. This paper was made with cooperation with firm Commerc Service spol.s.r.o., Prešov.