Dendrite growth kinetics of undercooled Iron-based alloy melts

Kurzfassung

Dendritic growth is the major crystal growth mode controlling the evolution of the microstructure during solidification of metallic alloys. In order to verify models for dendritic growth in undercooled melts growth velocities were measured on pure Fe and Fe-based alloy melts. We analyse the effect of solute redistribution on the growth of Fe-B revealing a small partitioning coefficient. Electromagnetic levitation technique is applied to undercool droplets of metallic melt accessible for in-situ diagnostics of the solidification processes. Deep undercoolings of more than 200 K prior to solidification are achieved, which leads to rapid growth of dendrites with velocities of several m/s. The temperature-time profile is measured by a pyrometer while rapid solidification is monitored by a high-speed video camera. The contrast between the liquid and solid phase is visible due to the release of latent heat during recalescence. Experimental results will be presented and discussed in the frame of current model for dendritic growth in undercooled melts. This research work is supported by the German Research Foundation DFG within contract HE1601/18 and ESA within the project CCEMLCC under contract no. 4200020277.