Metal Additive Manufacturing Conference 2018

T. Gan, A. Kao and K. Pericleous Centre for Numerical Modelling and Process Analysis Old Royal Naval College, Park Row University of Greenwich, UK, SE109LS Abstract Thermoelectric currents have been shown to exist in a wide range of solidification processes from rapid high undercooled growth [1] to casting and directional solidification [2]. These currents form through the Seebeck effect and are dependent on the thermal gradient. In the presence of an external magnetic field, a Lorentz force is generated through interaction of these currents and the field, driving fluid flow in the liquid melt. This type of flow, known as Thermoelectric Magnetohydrodynamics (TEMHD), is known to alter microstructural evolution through convective transport of heat and mass. Metal additive manufacturing (AM) and related processes such as welding, share many similarities in processing conditions to undercooled growth and directional solidification. Preliminary calculations show that TEMHD may have a profound effect in AM processes due to the inherently large thermal gradients, significantly altering the melt pool morphology. However, the distribution of thermoelectric currents and the resulting behaviour of the Lorentz force is not well understood. By using a purpose built computational model that couples various physical phenomena including solidification, electromagnetism and fluid flow, this paper investigates the macroscopic behaviour of the power bed fusion AM process and how key operating parameters determine the resulting TEMHD flow. References [1] A. Kao, J. Gao and K. Pericleous, Thermoelectric magnetohydrodynamic effects on the crystal growth rate of undercooled Ni dendrites, Philosophical Transactions of the Royal Society A (2018), Vol 376, Issue 2113. [2] J. Wang et. al, Modification ofliquid/solid interface shape in directionally solidifying Al–Cu alloys by a transverse magnetic field, J.Mater.Sci., 48–1 (2013), 213–219.