The transformation of liquid–solid interface induced by the steady magnetic field (SMF) in the directionally solidified Ni-10 wt pct Cr alloy was studied experimentally. At the moderate pulling rate (50 μm s⁻¹), it could be observed that the interface morphology gradually transformed from planar to cellular shape with increasing the SMF intensity (0 T, 3 T, 6 T). However, the cellular interface at the high pulling rate (100 μm s⁻¹) was not influenced by the SMF. 3D numerical simulations suggested that the transformation of interface morphology originated from the thermoelectric magnetic convection near the wavelike interface at the early stage of solidification. From the composition measurement, it was found that the formation of microsegregation at the moderate pulling rate was associated with the interface morphology. Under the 3 T SMF, the liquid–solid interface remained planar and the microsegregation level increased in comparison with that without the SMF. Under the 6 T SMF, the liquid–solid interface became cellular and the microsegregation level was reduced. The factors affecting microsegregation were evaluated. The effective partition coefficient was estimated based on composition data. It was revealed that the effective partition coefficient increased with the 6 T SMF due to the thermoelectric magnetic and magnetic damping effects within the cellular structure. Additionally, the solid diffusivity was measured using the diffusion couple technique. It was found that the interdiffusion coefficient of Cr decreased with increasing the SMF intensity. The modified Brody model was used to predict the microsegregation behavior in the SMF. The predicted results were in agreement with experimental observation. It could be concluded that the decrease in solid diffusivity enhanced the formation of microsegregation for the planar interface, whereas the increase in effective partition coefficient in the SMF was beneficial for alleviating the extent of microsegregation for the cellular interface.

实验研究了在定向凝固的Ni-10 wt pct Cr合金中，由恒定磁场（SMF）引起的液固界面的转变。在中等拉速（50μms ^-1）下，可以观察到随着SMF强度（0 T，3 T，6 T）的增加，界面形态逐渐从平面形状变为细胞形状。但是，细胞界面处于高拉速（100μms ^-1）不受SMF的影响。3D数值模拟表明，界面形态的转变起源于凝固初期波状界面附近的热电磁对流。从组成测量，发现在中等提拉速率下微偏析的形成与界面形态有关。与没有SMF的情况相比，在3 T SMF下，液-固界面保持平面，微偏析水平提高。在6 T SMF下，液固界面变成了细胞，微偏析水平降低了。评价了影响微偏析的因素。根据组成数据估算有效分配系数。结果表明，有效分配系数随着6 T SMF的增加而增加，这归因于蜂窝结构内的热电磁和磁阻尼效应。另外，使用扩散偶技术测量固体扩散率。发现随着SMF强度的增加，Cr的扩散系数降低。修改后的Brody模型用于预测SMF中的微偏析行为。预测结果与实验观察一致。可以得出结论，固体扩散率的降低促进了平面界面微偏析的形成，而SMF中有效分配系数的增加有利于减轻细胞界面微偏析的程度。