Effect of traveling magnetic field on solute distribution and dendritic growth in unidirectionally solidifying Sn–50 wt%Pb alloy: An in situ observation

Synchrotron X-ray radiography was used to in situ study the solute distribution and the dendritic growth during the bottom-up solidification of Sn–50 wt%Pb alloy under a traveling magnetic field (TMF) for the first time. The buoyance driven evolution and motion of the plumes containing Sn-rich melt are directly observed in the solidification front before the application of TMF. A forced melt flow from left to right is induced with the application of TMF, which results in the redistribution of the solute concentration (facilitate the solute transportation and reduce the local fluctuations considerably) and the change of the dendrite morphologies (promote/suppress the growth of the secondary arms, remelting and fragmentation of dendrites). Meanwhile, the concentration variations of Sn around the solidification front are quantitatively analyzed through the extraction of gray level from sequenced X-ray images.