Abstract
Melt pools formed in laser additive manufacturing (AM) are subject to large thermal gradients, resulting in the formation of thermoelectric currents due to the Seebeck effect. When in the presence of an external magnetic field, a Lorentz force is formed which drives fluid flow in the melt pool. This Thermoelectric Magnetohydrodynamics (TEMHD) phenomenon, can have a significant impact on the melt pool morphology and can alter the microstructural evolution of the solidification process. By coupling steady-state mesoscopic melt pool calculations to a microscopic solidification model, predictions of the resulting microstructure for multiple deposited layers have been obtained. The results indicate that the magnetic field can have a transformative effect on the microstructure and solute redistribution. This study highlights the theoretical potential for using magnetic fields as an additional control system to tailor AM microstructures.
Highlights
Additive Manufacturing (AM) is the process of creating complicated 3d objects by joining materials together, typically in a layer-by-layer approach
The results indicate that the magnetic field can have a transformative effect on the microstructure and solute redistribution
The computational domain is a cuboid with 800 μm in the scan direction, x, 300 μm in the build direction, z, and 600 μm in the magnetic field orientation, y
Summary
Additive Manufacturing (AM) is the process of creating complicated 3d objects by joining materials together, typically in a layer-by-layer approach. For the AM processing of metals, a high energy source, such as a laser, is used to melt metallic powder layers successively onto each other. This allows them to join as they solidify. A common AM process is selective laser melting (SLM) [1], which successively melts a thin layer of powder on the print bed These techniques create a liquid melt pool that travels with the energy source and solidifies in its wake. As the melt pool solidifies a microstructure is formed; this is modified or remelted as the scan is repeated for other layers This repeated remelting of layers leads to a number of defects that affect the integrity of components. This paper explores a novel control mechanism that has the potential to eliminate some of these defects
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