Abstract
The recent trend of using aluminium alloys instead of steel has reached the transportation industry, where increasingly, more parts are made of aluminium. An example is the belt pulley, applied for combustion engines for energy transmission. This part should be strong, durable, and lightweight. Aluminium-silicon alloys are a good choice, moreover, even when the surface is anodised, also because of their moderate inertia control and excellent wear characteristic during mechanical operations. Since aluminium is lightweight yet mechanically durable and anodised, it is an ideal belt pulley to use, especially in high-temperature operations. However, the main question is what type of Al-Si alloy, casting method and anodisation method should be used in terms of energy adsorption, having long-term properties for a lifetime, has to be applied. For this reason, this paper presents the influence of the chemical composition, casting method and anodising parameters on the structure and thickness of the anodic layer produced on aluminium alloys, as well as on the albedo value as an ability to reflect or absorb light. The aluminium alloys, AlSi12Cu1 and AlSi9Cu3, were used as research materials, obtained using different casting methods. The goal of this work was to determine the optimal combination of the anodisation conditions and materials for maximising the reflectivity factor of the surface, as a very important factor, determining the energy amount absorbed by an anodised surface. For further improvement of these surface properties as well as for enhancement of the properties and strengthen the material produced with different aluminium alloys production methods, different alloying additives were added. In addition, the mechanical properties of the surface layer were measured, where a remarkable hardness increase was obtained, and the best combination in form of AlSi12Cu1 high pressure cast was found with the highest albedo factor among all tested surface variants.
Highlights
In recent years, a continuous increase in the use of aluminium alloys across industries has been observed
Protective and decorative anodic coatings are applied to aluminium household goods, electronic components, parts of musical instruments, garden furniture, tourist and sports equipment, automotive accessories and aluminium joinery elements
Oxide coatings are produced on aluminium foil intended for electrodes in capacitors
Summary
A continuous increase in the use of aluminium alloys across industries has been observed. Oxide coatings are produced on aluminium foil intended for electrodes in capacitors. Hard anodic coatings are used in the aviation and transportation industries, where the effect on environmental pollutions is increasingly discussed [1,2,3]. Anodic oxide coatings permanently bonded to the aluminium substrate are corrosion resistant [4]. Corrosion resistance can be reduced by pores in the coating or by the presence of harmful alloying elements and impurities, especially copper. The intermetallic phases of copper with aluminium dissolve during anodising, which reduces the hardness and thickness of the coatings, increasing the porosity. During the formation of aluminium oxide, there is a slight increase in the mass of the workpiece and its volume. Dissolution of the oxide layer is possible only in alkaline or acidic solutions with a pH greater than 8.8 or less than 4.0 [5]
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