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Effect of Fe and Mn on corrosion resistance of recycled self-hardening AlZn10Si8Mg alloy

Mikolajčík Martin, Tillová Eva, Kuchariková Lenka, Šurdová Zuzana

Production Engineering Archives

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2025

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Vol. 31, Iss. 1

54--64

EN

Recycled aluminium alloys are a highly valued alternative for manufacturers, particularly in the automotive and aerospace industries, due to increasing demands on the environmental performance and sustainability of the industry. Self-hardening aluminium alloys, which achieve the required mechanical properties without heat treatment, enable the emissions generated by production to be reduced even further. In addition to an advantageous strength-to-weight ratio and excellent machinability, corrosion resistance in a variety of environments is also important in most applications of aluminium alloys. Repeated recycling cycles negatively influence the quality of aluminium because of an increase in iron content, which is considered an impurity. This is due to the formation of intermetallic phases which negatively affect the mechanical, fatigue and corrosion properties. In this paper, the effect of Fe and Mn on the microstructure and corrosion resistance of self-hardening recycled AlZn10Si8Mg alloy was investigated using the AUDI test, atmospheric long-terming test and 3.5% NaCl solution test. The corrosion mechanism was subsequently determined by sectioning the samples. Alloy A with the lowest iron content exhibited the best corrosion behaviour, as it was subjected to only localised forms of corrosion even in the aggressive environment of the AUDI test. In this environment, the other alloys were attacked by general corrosion of the entire surface. Manganese alloying caused a subtle improvement in the corrosion resistance of alloy D but was limited by the high porosity. The eutectic and intermetallic phases corroded the most, while the alpha phase was more resistant.

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Various metallography techniques for microstructure analysis of Ni-based superalloys

Belan Juraj, Uhríčik Milan, Mikolajčík Martin, Šurdová Zuzana

System Safety : Human - Technical Facility - Environment

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2024

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Vol. 6, iss. 1

473--484

EN

The Ni-based superalloys are known for the number of phases presented in alloy microstructure. Depending on alloying elements, phases such as austenitic FCC gamma matrix, L12 gamma prime, DO22 gamma double prime, BCT delta phase, and MC or M23C6 (or M6C) carbides have occurred. With these microstructure components' variety, the usual optical microscopy analysis is not satisfactory many times. For a better understanding of how single structures affect the lifetime of Nibased superalloys components (turbine blades or turbine discs) and how they are changing during their operation load is SEM a very powerful tool. Two different types of superalloys were used for experimental evaluation. The first were cast superalloys ZhS6K and IN 738. Both cast superalloys in bar form were subjected to additional heat treatment at 800°C for 10 and 15 hours followed by air-cooling. The influence of gamma prime phase morphology changes on alloy lifetime and Vickers hardness were evaluated by SEM coherent testing grid methods. The second was wrought superalloy IN 718 and Nimonic 80A in bar form to present the various grain size evaluation techniques according to ASTM E112 standards. Various analyses were employed (SEM fractography, BSE observation, EDS mapping, etc.) for microstructure evaluation. The main goal is to show how effective light microscopy and SEM on Ni-based superalloy analysis are when microstructure change evaluation is needed.

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The study of porosity in a356 secondary aluminium alloys with higher iron content

Šurdová Zuzana, Tillová Eva, Kuchariková Lenka, Mikolajčík Martin

System Safety : Human - Technical Facility - Environment

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2024

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Vol. 6, iss. 1

430--438

EN

The production of secondary (recycled) aluminium has gained significant importance in recent years, driven by the need to reduce electricity consumption and waste associated with primary aluminium production. Secondary aluminium alloys thus play a vital role in sustainable industrial practices, particularly within sectors such as automotive, aerospace and marine. Recently, these alloys have gained traction in electric vehicle components manufacturing, where lightweight and sustainable materials are critical to enhancing energy efficiency and extending vehicle range. However, secondary aluminium alloys are prone to impurities and casting defects, notably porosity, which presents challenges in achieving optimal mechanical properties and surface quality. Porosity reduces corrosion resistance, fatigue, and tensile strength, thus impacting overall material performance. This porosity can be categorised by size (microporosity and macroporosity) and origin, with gas and shrinkage porosity being the primary types. This study examined experimental A356 secondary aluminium alloys with varying iron contents in as-cast and T6 heat-treated conditions. The analysis focused on the quantitative assessment of casting defects within the microstructure, specifically, the types of pores present, the area percentage of pores, and average pore size. These insights contribute to a deeper understanding of how casting defects impact the performance of recycled aluminium alloys in sustainable applications, particularly in the context of nextgeneration electric vehicles.