Nowadays, a transportation industry creates a lot of metal scrap because production and use of cars are on the increase worldwide. This is based on the fact that increase in the production of cars increases usage of aluminium alloys in transportation applications. Therefore, it is necessary to reduce the production of components from primary aluminium alloy and increase their replacement with secondary-recycledaluminium alloys because the production of recycled aluminium alloys is less expensive and less energy-intensive than the creation of new aluminium alloy through the electrolysis. In addition, the recycled aluminium alloys have comparable microstructural parameters and properties as the same primary aluminium alloys. RECYCLING UND EIGENSCHAFTEN VON SEKUNDÄRALUMINIUM LEGIERUNGEN FÜR VERKEHRSINDUSTRIE Zusammenfassung. Dank weltweiter Produktionserhöhung und Benutzung der Fahrzeuge produziert die Verkehrsindustrie heute viel Metallabfall. Wie steigert die Fahrzeugerzeugung, so steigert auch die Benutzung von Aluminiumlegierungen. Es ist nötig, die Produktion von Aluminiumprodukten aus Primäraluminium zu reduzieren. Die Produkte müssen also durch die Produkte aus Sekundäraluminium eingesetzt werden. Während die Schmelzflusselektrolyse bei der Gewinnung von Aluminium aus Bauxit 100 Prozent Energie verbraucht, sind es beim Recycling etwa vier bis sechs Prozent. Das Aluminium-Recycling leistet deshalb einen beträchtlichen Beitrag zur Einsparung von Energie, und dient damit gleichzeitig auch dem Umweltschutz. Noch dazu, die Legierungen vom Sekundäraluminium haben vergleichbare Eigenschaften wie dieselben Legierungen von Primäraluminium.
Aluminum alloys are the most important part of all shaped castings manufactured, especially in the aerospace and automotive industries. This work focuses on the corrosion properties of the heat-hardening aluminum alloys commonly used for production of automotive castings AlSi7Mg0.3 and on self-hardening AlZn10Si8Mg. Iron is a common impurity in aluminum cast alloy and its content increases by using secondary aluminum alloys. Therefore, experimental materials were developed, with chemical composition according to standards (primary alloys) and in states with an increasing content of Fe. The experimental aluminum alloys are briefly discussed in terms of their chemical composition, microstructure, mechanical properties and corrosion behavior. Corrosion properties were examined using three types of corrosion tests: exposure test, potentiodynamic tests, and Audi tests. Corrosion characteristics of materials were evaluated using stereo, optical and scanning electron microscopy, energy dispersive X-ray analysis, too. Correlation of pit initiation sites with microstructural features revealed the critical role of iron-rich phases, silicon particles and corresponding alloy matrix.
In the present study, microstructure and porosity of AlSi7Mg0.3 cast alloy including various amounts (0.123; 0.454 and 0.655 wt. %) of iron were investigated. The alloys were produced as secondary (scrap-based -recycled IntroductionAutomotive -chassis, bodies, engine blocks, radiators, hubcaps, and etc. driven by consumer needs and increasingly tight regulations, the automobile industry has made ample recourse to aluminium. A European car today contains on average 100 kg of aluminium, taking advantage of multiple properties of the materials: lightness (a 100 kg loss of weight reduces fuel consumption by 0.6 litres/100 km and greenhouse gases by 20 %), resistance (improved road-handling, absorption of kinetic energy, shorter braking distance) and recycling (95 % of the aluminium contained in autos is collected and recycled, and represents over 50 % of the vehicle's total end-of-life value). Aluminium coming from recycling can allow 95 % energy savings and 85 % less CO 2 emissions compared to primary aluminium production. Recycling -aluminium can be recycled indefinitely without losing any of its intrinsic qualities. This is a considerable advantage in modern metallurgical industry. For the past 20 years the proportion of metal consumed that is recycled has grown steadily and today stands at something like 30 % of primary metal production (European Aluminium Association; Schlesinger, 2014;Hurtalová et al., 2013).The Fig. 1 shows the fraction of world aluminium production from primary and secondary (recycled) sources. About one-third of the aluminium produced in the world is now obtained from secondary sources and in some countries the percentage is much higher. The process used for recycling aluminium scrap is very much different from those used to produce primary metal but in many ways follow the same general sequence. This sequence begins with mining ore, followed by mineral processing and thermal pre-treatment and then a melting step. The metal is then refined, cast into ingots and sent to customers. Aluminium alloys recyclers also face similar challenges to the producers of primary aluminium; there is need to produce a consistent alloy with the required chemistry, reduce the amount of waste generated, minimize energy usage and manufacture the highest-quality product at the lowest possible cost from raw materials of uncertain chemistry and condition (Mc Millan et al., 2012;Schlesinger, 2014).Commercial Al-alloys always contain Fe, often as undesirable impurity and occasionally as a useful minor alloying
Corrosion resistance of sensitized austenitic stainless steel (SS) in chloride environments is currently the subject of numerous studies. Most of them are focused on neutral chloride solutions at room temperature and the experiments are carried out on ground stainless steels surfaces. This paper deals with the corrosion behavior of sensitized AISI 304 stainless steel in acid 1 M chloride solution (pH = 1.1) at the temperatures of 20 ± 3 °C and 50 °C. The specimens after sensitization are tested as covered by high-temperature surface oxides (“heat tinted”), and also after their chemical removal to assess the impact of the surface state on corrosion resistance. Potentiodynamic polarization (PP) and exposure immersion test are used as the independent corrosion tests. Microstructure before/after exposure immersion test is evaluated by optical microscopy (OM) and SEM. The results obtained showed that sensitization significantly conditions corrosion regardless of the removal of high-temperature oxides, and the elevated temperature mainly acts as its accelerating factor.
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