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Al-Bi偏晶合金是潜在的新型汽车轴瓦材料,然而由于偏晶合金的凝固特点,凝固过程中的液-液分离反应极易造成第二相的宏观偏析,很难采用传统凝固方法制备。在水平稳恒磁场下进行Al-Bi偏晶合金的水冷铜模浇铸实验,使熔体内不同位置的温度梯度方向与磁场方向呈不同角度。研究当磁场与富Bi液滴Marangoni运动方向的夹角不同时,磁场对偏晶合金凝固组织影响效果的变化。研究结果表明当磁场方向与富Bi相液滴Marangoni运动方向平行时,磁场对宏观偏析的抑制效果最明显。对本实验条件下磁场在Al-Bi偏晶合金凝固过程中的作用机制进行了分析,Al-Bi偏晶合金富Bi液滴发生了由冷端向热端的Marangoni运动,磁场主要通过电磁拖曳力作用于液滴,降低液滴的迁移速度。当磁场与温度梯度方向垂直时,其对熔体传热的抑制减小了电磁拖曳力的作用效果,加重了富Bi相液滴Marangoni运动造成的偏析。
However, due to the solidification characteristics of the meta-crystal alloy, the liquid-liquid separation reaction in the solidification process can easily cause macro-segregation of the second phase and is difficult to be prepared by the conventional solidification method. In the horizontal steady magnetic field Al-Bi monotectic alloy water-cooled copper mold casting experiment, so that the melt temperature in different locations and the direction of the magnetic gradient direction at different angles. The effect of the magnetic field on the solidification structure of the monotectic alloy is studied when the angle between the magnetic field and the Marangoni movement direction of the Bi-rich droplets is different. The results show that the magnetic field has the most obvious effect on macrosegregation when the direction of the magnetic field is parallel to the Marangoni movement direction of Bi-rich droplets. The mechanism of the magnetic field in the solidification process of Al-Bi monotectic alloy under the experimental conditions was analyzed. The Marangoni movement from cold end to hot end occurred in Bi-Bi-Bi amorphous alloy droplets. The magnetic field was mainly induced by electromagnetic drag force Droplets reduce the rate of droplet migration. When the magnetic field is perpendicular to the temperature gradient direction, the suppression of the heat transfer decreases the effect of the electromagnetic drag force and aggravates the segregation caused by the Marangoni movement of Bi-rich droplets.