Effect of Silicon Content on Solidification Parameters and Microhardness of Al–Si Alloys

In the present work, aluminumAluminum–silicon (Al-Si) hypoeutectic alloysAlloys were studied in order to investigate the effect of solidificationSolidification parameters due to the addition of Si in the range of 6 wt. % to 9 wt. % on the structure characteristics and the microhardnessMicrohardness. The study was made by directional solidificationDirectional solidification methodMethod in a Brigdman-type furnaceFurnace. Different types of grains (columnar, equiaxed, and with columnar to equiaxed transition, CET) were visually observed. Such CET depended on the critical thermal gradient Gtc. The analyses carried out indicate that the secondary dendritic spacing (λ2) and the grain size increase significantly with the decrease in the cooling rateCooling rate (Ve). Furthermore, it was observed that the resulting microhardnessMicrohardness increases as the solidificationSolidification parameters (specifically Ve) increase, this is due to a refinement of the macro and microstructural parameters. Also, it was observed that the microhardnessMicrohardness increased with the increase of the Si content.