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

Abstract

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.