Dendritic growth kinetics of undercooled Fe-B alloy melts

Abstract

In metallic alloys dendritic growth is the major crystal growth mode controlling the evolution of the microstructure during solidi�cation. The present work investigates the growth kinetics on pure Fe and Fe- B alloy melts in order to verify models for dendritic growth in undercooled melts. In detail, we analyze the e�ect of solute redistribution and solute trapping on the rapid growth of dilute Fe-1 at.% B alloy with B showing a small partitioning coe�cient. For in-situ studies on deeply undercooled melts electromagnetic levitation technique (EML) is used. The rapid solidi�cation is recorded by a high-speed camera. Undercoolings from 50 K to 300 K prior to solidi�cation leads to growth velocities of several cm/s up to m/s. Concerning terrestrial EML the electromagnetic �eld necessary for levitation induces strong convective uid ow inside the melt. To investigate the e�ect of convection on the growth kinetics experiments on parabolic ight are carried out under reduced gravity conditions. The microstructure of the solidi�ed sample is analyzed by SEM and EBSD. Experimental results will be presented and discussed in the frame of current models for dendritic growth in undercooled melts. This research work is supported by DFG contract HE1601/18 and by ESA under contract 4200020277 and 4200014980.