Thermochemical modelling and mechanical property of the Al-7.6Si-xZr alloy

This study utilised the gravity casting method to modify hypoeutectic Al-7.6Si alloys with Zr at varying weight percentages (0.1%, 0.2%, and 0.3%). The unmodified alloy typically consists of a needle or platelike eutectic silicon within the dendritic α-Al phase. The addition of Zr increases the liquidus temperature of the alloy and results in the formation of ZrSi and ZrSi2 compounds, which act as nucleation sites for both the eutectic Si and α-Al grains. As a result, the needle or platelike eutectic silicon transforms into a fibrous structure with a more uniform distribution, and the α-Al phase becomes finer and globular. These microstructural changes lead to improved bulk hardness, ductility, and mechanical properties of the alloy.