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.
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