通过对单晶高温合金定向凝固生长过程中显微组织的考察，研究了磁场下杂晶在籽晶回熔区附近的产生及其在生长过程中的演变机制。磁场使得定向凝固籽晶重熔区界面上出现大取向杂晶和大角度晶界，其多分布于样品边缘，磁场强度和抽拉速率的增大均增加了杂晶数量和大角度晶界长度。凝固起始阶段形成的大取向杂晶和大角度晶界以较快速率被淘汰，演化成小取向枝晶和小角度晶界；随着凝固继续进行，枝晶取向和晶界角度进一步减小，但是演化速率急剧降低，拉速的增大强化了此演变过程。重熔区界面上杂晶的形成是由于热电磁力对枝晶的扭断，而宏观尺度上的热电磁环流在凝固过程挟制着扭断碎晶，使得碎晶演化成较多分布于样品边缘的杂晶。

Nickel-based superalloys, especially single-crystal (SC) ones, have long been recognized as important materials for turbine blades used in aerospace and gas engines. Static magnetic fields are effective at controlling the material forming. The use of static magnetic fields during solidification has evolved as a sophisticated approach for efficiently controlling the microstructures and mechanical performance of metallic materials. In recent years, studies have shown that static magnetic fields have a complex effect on dendrites in SC superalloys. However, the mechanism of static magnetic fields regulating stray grains on remelted interface needs to be investigated further. This work studied the generation of stray grains near the seed remelted zone and the evolution mechanism during the directional solidification of the SC superalloy assisted by a magnetic field by tracing the solidification microstructure. The stray grains of large orientation that deviated from the <001> direction appeared on the remelted zone interface of the solidification microstructure when the magnetic field was applied, accompanied by the formation of a large-angle grain boundary (LAGB). Most of the stray grains were distributed at the sample edge. The increase in magnetic field intensity and pulling speed increased the number of stray grains and the length of the LAGB. As the solidification progressed, the large-orientation stray grains and the LAGBs were eliminated at a fast speed and evolved into small-orientation dendrites. During the following solidification, the orientation of the dendrites became even smaller and the evolution speed decreased sharply. The increase in withdrawal speed intensified the evolution process. The stray grains formed in the remelted zone can be attributed to the twisting dendrite by the thermoelectric magnetic force. The distribution of more stray grains around the sample was caused by the circulation from thermoelectric magnetic convection at the macroscopic scale.