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

Abstract

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.