Effects of Casting-Additives on the Microstructure Evolution of Hypoeutectic Aluminium-Silicon Alloys

Since the industries are called to produce environmentally friendly products, the research is moving toward new improved materials. In this panorama, aluminium alloys find applications for a large range of products. In the automotive, as well as in the aerospace, sector, aluminium alloys are largely adopted, thanks to their high specific properties and their light weight. Moreover, common casting techniques permit us to realize complex high-quality components. These components may be realized by using casting techniques adopting casting-additives, such as modifiers or refiners. In this work, the effect of refining and modification was studied in terms of microstructural evolution of the intermetallic phases in two aluminium-silicon alloys (EN AC 45300 and EN AC 43500). Microstructures were analyzed through micro-hardness measures, and we found a reduction in the standard deviation of the hardness with the addition of additives. Furthermore, secondary dendrites arms spacings (SDAS) were measured, evidencing a decrease in SDAS by adding casting additives. A strong correlation was found between the adding of additives and the possibility of containing the size of the silicon and of all the intermetallic phases opening up to the possibility of tailoring the microstructures.