摘要
The large and small sized Cu（solid）/Al（liquid） couples were prepared to investigate the directional growth behavior of primary a（Al） phase during a concentration-gradient-controlled solidification process under various static magnetic fields（SMFs）.The results show that in the large couples,the α（Al） dendrites reveal a directional growth character whether without or with the SMF.However,the 12 T magnetic field induces regular growth,consistent deflection and the decrease of secondary arm spacing of the dendrites.In the small couples,the α（Al） dendrites still reveal a directional growth character to some extent with a SMF of ≤5 T.However,an 8.8 T SMF destroys the directional growth and induces severe random deflections of the dendrites.When the SMF increases to 12 T,the a（Al） dendrites become quite regular despite of the consistent deflection.The directional growth arises from the continuous long-range concentration gradient field built in the melt.The morphological modification is mainly related to the suppression of natural convections and the induction of thermoelectric magnetic convection by the SMF.
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。
基金
Projects(51201029,51071042,51374067)supported by the National Natural Science Foundation of China
Projects(N130409002,N130209001)supported by the Research Funds for the Central Universities
Project(2012M520637)supported by the China Postdoctoral Science Foundation
