目的 研究热成形钢热浸镀铝硅镀层的微观组织与物相组成。方法 利用扫描电镜(SEM)和能谱仪(EDS)分析铝硅镀层表面与截面的微观组织形貌与成分，利用X射线衍射(XRD)和电子背散射衍射技术(EBSD)分析铝硅镀层的物相组成与比例。结果 热浸镀铝硅镀层表面由富Al相、少量的富Fe相以及树枝晶网状分布的高Si相构成，截面是由内外两层组成，其靠近铁基体的内层为Fe-Al-Si合金层，外层为Al-Si层。进一步的研究显示，Al-Si层由富Al相、少量的富Fe相以及柱状分布的高Si相构成，高Si相主要存在于合金层与铝硅层界面以及Al-Si层中。结论 热浸镀铝硅镀层中富Al相、富Fe相、高Si相和Fe-Al-Si三元合金层的物相分别为Al、Al13Fe4、Si和Al8Fe2Si。对热浸镀铝硅镀层中高Si相的研究显示，分布于合金层与铝硅层界面处的高Si相，可以有效阻碍镀层的生长，而分布于铝硅层中的高Si相在空间中以立体网状骨架的结构形式存在，这种立体网状结构形式作为镀层的主体框架，可以有效地提高镀层的强韧性和成形性能。

This paper aims to study the microstructure and phase composition of hot-dip Al-Si coating on hot-formed steel. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were used to analyze the microstructure and composition of the surface and cross-section of the Al-Si coating; X-ray diffraction (XRD) and electron backscatter diffraction (EBSD) were used to analyze the phase composition and ratio of the Al-Si coating. The surface of the hot-dip Al-Si coating is composed of Al-rich phase, a small amount of Fe-rich phase, and high Si phase with dendritic network distribution; the cross-section of the hot-dip Al-Si coating is composed of inner and outer layers, the inner layer close to the iron matrix is an Fe-Al-Si alloy layer, and the outer layer is an Al-Si layer. Further research shows that the Al-Si layer is composed of Al-rich phase, a small amount of Fe-rich phase, and columnar distributed high Si phase; the high Si phase mainly exists at the interface between the alloy layer and the Al-Si layer and in the Al-Si layer. The phases of Al-rich phase, Fe-rich phase, high Si phase and Fe-Al-Si ternary alloy layer in the hot-dip Al-Si coating are Al, Al13Fe4, Si and Al8Fe2Si respectively. The study of high Si phase in hot-dip Al-Si coating has shown that the high-Si phase distributed at the interface between the alloy layer and the Al-Si layer can effectively hinder the growth of the coating, while the high-Si phase distributed in the Al-Si layer exists in the form of a three-dimensional network framework in space. This three-dimensional network structure as the main frame of the coating can effectively improve the strength and toughness and formability of the coating.