凝固过程显著影响着材料的微观组织和成分分布，从而影响产品最终性能。 形核作为凝固过程的初始阶段，极大地影响了后续相的生成次序、相组成、晶粒大小及分布，对材料的最终性能有不可忽视的影响。 磁场是凝固过程的重要调控手段，磁场下的金属形核研究对于通过磁场调控金属凝固过程微观组织研究具有重要意义。 目前关于磁场对形核行为的影响研究较为有限，多以对宏观现象的观测为主，局限于定性解释，缺乏对微观尺度的异质形核现象和磁场作用机理的深入探究。 本文综述了金属凝固过程形核理论、模型及形核过程的研究现状，详细介绍了磁场下金属凝固过程形核行为的研究进展，并提出了磁场作用下形核研究的发展方向。

The microstructure and composition distribution of the material are significantly influenced by the solidification process, thus affecting the final properties of product. As the initial stage of solidification process, nucleation greatly influences the order of subsequent phase formation, composition, grain size and distribution, and has a non-negligible impact on the final properties of the material. The magnetic field is an important method to modify the solidification process. Therefore, the study of nucleation under magnetic fields is of great importance to tune the microstructure during metal solidification via applied magnetic field. However, the current researches are very limited, mostly focused on the macroscopic experimental phenomena, which can only provide qualitative explanations, lacking in-depth investigation on heterogeneous nucleation process and magnetic field mechanism at the microscopic scale. In this paper, research status of nucleation theory, models and nucleation processes is introduced, followed by the current situation on solidification processes of metals under magnetic fields, and the development directions are proposed.