电场调控下合金凝固过程枝晶形貌演变同步辐射原位成像

由于金属合金的不透明性, 研究者们无法实时捕捉到金属合金凝固过程中枝晶生长的动态行为, 也无法直接观察到电流对枝晶生长行为的动态调控过程. 采用同步辐射X 射线成像技术, 实时观察到了电流对枝晶生长形貌演变的动态调控过程. 成像结果表明, 直流电流能够显著抑制枝晶生长, 并促使枝晶尖端变平,随着电流增加, 枝晶尖端发生分裂现象, 这归因于枝晶尖端的电流拥挤以及溶质富集. 脉冲电流能够显著细化枝晶臂间距并影响其凝固进程, 主要原因是周期性的脉冲电流对液固界面产生了循环的热冲击和振荡扰动所致.

Real time imaging on dendrite morphology evolution during alloy solidification under electric field

The evolution of dendrite morphology during the solidification of metallic alloy can not be in-situ observed since the metallic alloy is in optically opaque. It is also not possible to in-situ study the influence of electric current on dendritic growth behavior. By using synchrotron radiation imaging technique, we observe the evolution of dendrite morphology under an electric current. The imaging results indicate that the direct current can significantly suppress the dendritic growth. The dendrite tip turns to be round from sharp under direct current. With the increasing of current intensity, the dendrite tip splits due to the current crowding and solute pileup around the round tip. The pulsed electric current can significantly enhance the solidification rate and refine the primary and secondary dendrite arm spaces because of the thermal and mechanical shock around solid/liquid interface.