ABSTRACT The process of multistep nucleation during solidification in hypoeutectic Al-Mg-Si casting alloys was investigated. The morphology of the nucleating particles, Mg2Si primary crystals and Al-Mg2Si eutectic, was investigated with scanning electron microscopy (SEM) on polished and deep etched microsections. The mechanism of formation of the Mg2Si crystal was attributed to heterogeneous nucleation on the nucleating particles. It was observed that the majority of the alloys particles found in the studied are oxides. It was established that eutectic Al–Mg2Si in hypoeutectic alloys has the morphology of ‘eutectic crystal’, where one face of the crystal has triangular-spiral morphology. The mechanism of formation of Al-Mg2Si eutectic cells is attributed to epitaxial growth on Mg2Si crystals. The microhardness of the structural components (Mg2Si crystals, α-Al dendrites, Al-Mg2Si eutectic, and Al3Ti crystals) was measured using Vickers hardness tester.

中文翻译：

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铸造 Al-Mg-Si 合金的组织形成和多步形核

摘要 研究了亚共晶 Al-Mg-Si 铸造合金凝固过程中的多步形核过程。用扫描电子显微镜 (SEM) 在抛光和深度蚀刻的显微切片上研究成核颗粒、Mg2Si 初晶和 Al-Mg2Si 共晶的形态。Mg2Si 晶体的形成机制归因于成核颗粒上的异质成核。据观察，在研究中发现的大多数合金颗粒是氧化物。已确定亚共晶合金中的共晶 Al-Mg2Si 具有“共晶晶体”的形态，其中晶体的一个面具有三角形螺旋形貌。Al-Mg2Si 共晶晶胞的形成机制归因于 Mg2Si 晶体上的外延生长。