Undercooling and solidification of liquid metals under different conditions of convection

• Applicant: Professor Dr. Dieter M. Herlach (†)
• Subject Area: Mechanical Properties of Metallic Materials and their Microstructural Origins
• Term: from 2007 to 2009
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 34773604

Undercooling of liquid alloys leads to non-equilibrium solidification with the formation of metastable materials of properties being different to them of their stable counterparts. So-lidification of undercooled melts is controlled by heat and mass transport in front of the solid-liquid interface. In case of undercooled melt any planar interface is unstable and one has to deal with dendritic morphology of the solidification front. Both size and morphology of dendrites are essentially influenced by fluid flow in the interdendritic regime of the liquid. Effects of morphological instability and fragmentation of growing dendrites even leads to the formation of highly grain refined and equiaxed microstructures with essentially im-proved mechanical, magnetic and electrical properties.In the present project it is aimed to test various parameters to control the interdendritic fluid flow motion during solidification of undercooled melts. We envisage studying the evo-lution of microstructures as a function of undercooling under the conditions of strongly forced convection in alternating electromagnetic fields by electromagnetic levitation, natu-ral convection by processing the melt in a melt fluxing medium and with highly reduced convection by performing undercooling and solidification experiments in reduced gravity. In addition to that our Chinese project partner, Professor Jianrong Gao from Key Laboratory of Electromagnetic Processing of Materials, Northeastern University, Shenyang will per-form comparative experiments, however, utilizing strong electromagnetic fields up to 12 Tesla to test their influence of damping of fluid flow motion for microstructure control dur-ing solidification of undercooled melts. We choose Cu-Ge and Cu-Co alloys as proper sample material for our investigations.

• DFG Programme: Research Grants
• International Connection: China
• Participating Persons: Professor Dr. Jianrong Gao; Dr. Sven Reutzel