Effect of Si, Cu, Mn additions on the extrudability of recycled Al-Zn-Mg alloys

Abstract

With the growing demand for lightweight materials and the increasing focus on low-carbon footprint policies, aluminum recycling has become a critical concern in recent years. Despite advancements in sorting techniques, the recycling process can still result in modifications and variations in alloy composition due to the introduction of impurities. This study investigates the extrudability of the Al-Zn-Mg alloy (7108 alloy) with the addition of Si, Cu, and Mn elements. To assess extrudability, a 9 mm in diameter rod profile with two 1×1 mm² fins on each side was meticulously designed. Extrusion trials at varying speeds were conducted using a laboratory extrusion press. The results indicate that the addition of 0.22% Si reduces the maximum allowable extrusion speed before tearing occurs but also lowers the required press load by forming coarse Mg2Si particles. Adding Cu up to 0.17% has a minor effect on extrudability and extrusion load. In contrast, the addition of Mn significantly enhances extrudability by capturing Si into AlMnSi particles, which exhibit stable thermomechanical properties. These findings highlight the potential for incorporating higher impurity levels in aluminum alloys without compromising extrudability, thereby supporting the development of advanced extrusion products using recycled alloys.