强磁场下Cu-50%Ag合金定向凝固过程中的组织及固液界面形貌演变

目的 研究强磁场下Cu-50%(质量分数)Ag合金定向凝固过程中的组织演变、固液界面形貌变化及溶质迁移行为，分析强磁场对金属凝固过程的作用机制，为强磁场下的金属材料制备提供理论借鉴和指导。方法 在不同的凝固速率与磁场条件下进行定向凝固和淬火实验，对合金的定向凝固组织、糊状区与固液界面形貌以及溶质分布行为进行考察。结果 强磁场破坏了凝固组织的定向生长，使凝固组织转变为枝晶与等轴晶共存的形貌;强磁场诱发了熔体对流，减少了糊状区中溶质的含量;强磁场改变了固液界面处的溶质分布和固液界面形貌，破坏了固液界面的稳定性。结论 强磁场通过洛伦兹力和热电磁力的共同作用，诱发了糊状区内液相的纵向环流，改变了固液界面及糊状区中的组织形貌与元素分布。

Evolution of Microstructure and Solid-liquid Interface of Cu-50%Ag Alloy during Directional Solidification under High Magnetic Field

The work aims to study the microstructure evolution, morphology changes of solid-liquid interface and solute migration behavior of Cu-50wt.%Ag alloy during directional solidification under high magnetic field and analyze the effect mechanism of high magnetic field on metal solidification, so as to provide theoretical reference and guidance for preparation of metal materials under high magnetic field. The solidified microstructure, mushy zone, solid/liquid interface morphology and solute distribution behavior of the alloy were investigated by directional solidification experiments under different solidification rates and magnetic fields. Under the high magnetic field, the directional growth of the solidified microstructure was destroyed and the morphology of solidified microstructure was transformed to the coexistence of dendrites and equiaxed crystals. The high magnetic field induced melt convection and reduced the solute content in the mushy zone. The high magnetic field changed the solute distribution and the morphology of the solid-liquid interface, and destroyed the stability of the solid-liquid interface. The high magnetic field induces the longitudinal circulation of liquid phase in the mushy zone through the combined action of Lorentz force and thermoelectric magnetic force, which changes the microstructure and element distribution at the solid-liquid interface and in the mushy zone.