In the foundry industry, commercial Al-Si alloys are among the most commonly used for casting various products. The main reasons for this are primarily their excellent mechanical, thermal-physical, and metallurgical properties, as well as their excellent castability. The foundation for the desired properties is the initial microstructure, which determines how suitable the resulting casting will be in relation to the required properties.
The most important property of silicon, which is why it is added to aluminum, is hardness and the lowering of the eutectic temperature. However, the drawback of silicon is the sharp edges of eutectic silicon particles, which significantly reduce the ductility of the alloys. The preferred morphology is rounded and has better properties, as it is more similar to a fibrous structure. This is achieved through a modification process, which can be done thermally, by rapid cooling, or chemically by adding modifying elements to the melt. In the aluminum foundry industry, strontium and sodium have proven to be the best modifiers. Strontium is added as an AlSr master alloy in the form of rods, while sodium is added in the form of salt. Additionally, the strength of aluminum alloys can also be improved through heat treatments such as T5 and T6, which are based on artificial aging.
In the experimental part, we will perform the process of adding both modifiers in different amounts, followed by heat treatments T5 and T6. The prepared samples will be analyzed using light and electron microscopy, and mechanical property tests will be conducted. The obtained results will be compared, and a summary will be provided. Based on the results, the suitability and effectiveness of each modifier will be evident, and we will also determine at which modifier content the modification process was most successful.
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