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制备大小两种Cu(固态)/Al(液态)扩散偶,考察在不同静磁场下浓度梯度控制的凝固过程中初生α(Al)相的定向生长行为。结果表明:在大扩散偶中,无论是否施加磁场,α(Al)枝晶均呈现定向生长特征,但12T磁场导致枝晶的规则生长、一致偏转和二次枝晶臂减小;在小扩散偶中,当磁感应强度≤5T时,α(Al)枝晶仍呈一定的定向生长特征,当磁感应强度升至8.8T时,枝晶的定向生长被破坏并诱发严重的混乱偏转,而当磁感应强度升至12T时,枝晶尽管仍呈一致偏转,但变得非常规则。枝晶的定向生长源于在熔体中建立的连续长程浓度梯度。枝晶的形貌改变则主要与静磁场对自然对流的抑制以及其诱发的热电磁对流有关。
Two kinds of Cu (solid) / Al (liquid) diffusers of different sizes were prepared to investigate the directional growth behavior of primary α (Al) phase during concentration gradient controlled solidification under different static magnetic fields. The results show that the growth of α (Al) dendrites shows directional growth regardless of whether a magnetic field is applied or not, but the regular growth of dendrites, the uniform deflection and the dendrite arm decrease with the application of 12T magnetic field. Even when the magnetic induction intensity is less than or equal to 5T, the α (Al) dendrites still show some directional growth characteristics. When the magnetic induction increases to 8.8T, the directional growth of dendrites is destroyed and induced serious disorder deflection. When the strength rises to 12T, the dendrites, though still uniformly deflected, become very regular. The directional growth of dendrites stems from the continuous long-range concentration gradient established in the melt. The morphology of dendrites is mainly related to the suppression of natural convection by the static magnetic field and the induced thermo-electromagnetic convection.