Abstract
<title>Abstract</title> <p>Al7Si0.3Mg alloy is a typical representative of hypoeutectic Al-Si alloys. Owing to its low density, high specific strength and excellent castability, it is extensively applied in the manufacture of lightweight components in the aerospace and automotive industries. However, iron impurity in the alloy tends to form needle-shaped β-Al5FeSi iron-rich phases, which cut through the aluminum matrix and deteriorate the microstructure and mechanical properties of the Al7Si0.3Mg alloy. This work takes Al7Si0.3Mg alloys with Fe content in the range of 0.2 wt.% to 1.2 wt.% as the research object, and systematically investigates the influence of Fe content on the microstructure and properties of the alloy. In industrial production, a certain proportion of Fe is commonly introduced into the alloy to improve demolding performance and prevent aluminum melt from adhering to mold steel. Although Fe is generally regarded as an impurity element in aluminum alloys, appropriate Fe content can induce the formation of stable iron-rich phases such as α-Al(Fe,Mn)Si and β-AlFeSi. These phases can pin grain boundaries to a certain extent, enhance the high-temperature stability of the alloy and reduce its thermal cracking tendency. Nevertheless, once the Fe content exceeds the critical threshold, a large number of coarse, acicular and plate-like β-AlFeSi phases will precipitate along grain boundaries in a network distribution, which severely damages the continuity of the alloy matrix and becomes the initiation site of cracks, ultimately leading to a significant reduction in the ductility, impact toughness and fatigue life of the alloy. To resolve the above-mentioned scientific and engineering problems, this paper adopts scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and room-temperature tensile testing to systematically investigate the effect of Fe content variation on the evolution behavior of iron-rich phases, as well as the microstructure and properties of commercial cast Al7Si0.3Mg alloys in Al-Si-Mg system.</p>