In this paper, the diversity of complicated dendrite microstructure and its evolution behavior during solidification in different magnesium alloys under various processing conditions were illustrated using synchrotron X-ray imaging technique. A variety of dendritic morphologies and branching structures were revealed, i.e., sixfold plate-like symmetric structure in Mg–Al-based structure, 12-branch structure in Mg–Zn-based alloys and 18-branch structure in Mg–Sn- and Mg–Ca-based alloys as well as seaweed like hyper-branched structure in Mg-38wt%Zn alloy. In addition, a dendrite morphology and orientation transition with increasing addition of Zn content were also observed in Mg–Zn alloy, with dendrite growth pattern transform from anisotropy (low Zn addition) with sixfold symmetric snow-flake structure to relative isotropy (intermediate Zn addition) where seaweed morphology presented and then back to anisotropy (high Zn addition) when only 12 branches with preferred < 11 \(\overline{2}\) 1 > orientations were observed. The phase-field model representing the typical dendritic morphologies and branching structures under various conditions was also depicted and discussed. Further, the two-dimensional (2D) real-time dendrite growth dynamics in different Mg-based alloys captured using synchrotron X-ray radiography for unveiling the originate of the α-Mg dendrite was reviewed. Following this, the four-dimensional (3D + time) synchrotron X-ray tomographic in situ observation of dendritic morphology evolution indicating the formation mechanism of the diverse dendritic morphology during Mg–Sn- and Mg–Zn-based alloys was also summarized. Finally, the future study on exploring the complicated dendritic morphologies and their origination during solidification of Mg-based alloys is prospected.

本文利用同步加速器X射线成像技术阐明了不同镁合金在不同加工条件下凝固过程中复杂枝晶组织的多样性及其演化行为。揭示了各种枝晶形貌和分支结构，即Mg-Al基结构中的六重板状对称结构，Mg-Zn基合金中的12分支结构和Mg-Sn-和Mg中的18分支结构–Ca 基合金以及 Mg-38wt%Zn 合金中的海藻状超支化结构。此外，随着 Zn 含量的增加，在 Mg-Zn 合金中也观察到枝晶形态和取向转变，\(\overline{2}\) 1 > 方向被观察到。还描述和讨论了代表各种条件下典型树枝状形态和分支结构的相场模型。此外，还回顾了使用同步加速器 X 射线照相术捕获的不同镁基合金中二维 (2D) 实时枝晶生长动力学，以揭示 α-Mg 枝晶的起源。在此之后，还总结了四维（3D + 时间）同步加速器 X 射线断层扫描对枝晶形貌演变的原位观察，表明了 Mg-Sn 和 Mg-Zn 基合金中不同枝晶形貌的形成机制。最后，展望了未来探索镁基合金凝固过程中复杂枝晶形貌及其成因的研究。