The influence of thermoelectric magnetohydrodynamics in microstructure evolution


The influence of thermoelectric magnetohydrodynamics in microstructure evolution

Kao, A.; Attwood, R.; Clark, S.; Eckert, S.; Fan, X.; Gan, T.; Lee, P. D.; Pericleous, K.; Shevchenko, N.; Soar, P.; Tonry, C.

The application of a static magnetic field to alloy solidification has been shown to significantly influence microstructure evolution, through convective transport generated by the so-called thermoelectric magnetohydrodynamic (TEMHD) effect. Strong effects have been observed across a wide range of solidification length and time scales, from the slow growth of directional solidification to the rapid growth of undercooled solidification and additive manufacturing (AM). Observed changes to the microstructure reported include the generation of an ‘Archimedes’ screw during rotation, the control of channels responsible for ‘freckle’ defects, melt pool morphology in AM and influence of tip growth velocity. These changes have been observed experimentally and predicted numerically using our code TESA (ThermoElectric Solidification Algorithm), a bespoke parallelised microstructure solidification code that intimately couples the effect of the magnetic field and fluid flow through Cellular Automata and Lattice Boltzmann methods. TESA captures the interaction of key transport phenomena, competition of MHD flow with buoyancy and Marangoni driven convection and ultimately the effect on evolving microstructure across a wide range of processes.
This talk focuses on the effect of a magnetic field on channel formation in DS, and melt pool dynamics and solute redistribution in AM. A particularly interesting aspect of such phenomena is the inter-dependency of the thermo-solutal, hydrodynamic and electromagnetic problems. Thermoelectric (TE) currents are dependent on the temperature and solute distribution, which in turn through the convective transport influencing solidification alters the TE currents. This leads to an interesting consequence where both the temperature field (controlled externally as in DS or as a localised heat source in AM) and magnetic field have strong influences on the formation of TE currents and ultimately TEMHD. This coupling of temperature and magnetic field potentially opens many avenues for novel control techniques in solidification.

Keywords: Thermoelectric magnetohydrodynamics; Microstructure solidification; Magnetic field; Convective transport

  • Invited lecture (Conferences)
    The 6th International Conference on Advances in Solidification Processes, ICASP-6, 20.-24.06.2022, Bischoffsheim, France

Permalink: https://www.hzdr.de/publications/Publ-33935
Publ.-Id: 33935