Fan, Xianqiang;
Fleming, Tristan G;
Clark, Samuel J;
Fezzaa, Kamel;
Getley, Anna CM;
Marussi, Sebastian;
Wang, Hongze;
... Lee, Peter D; + view all
(2025)
Magnetic modulation of keyhole instability during laser welding and additive manufacturing.
Science
, 387
(6736)
pp. 864-869.
10.1126/science.ado8554.
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Abstract
Keyhole instability during laser welding and laser powder bed fusion (LPBF) can cause keyhole collapse and pore formation. Using high-speed x-ray imaging, we demonstrate that the flow vortex-induced protrusion on the rear keyhole wall is crucial in initiating keyhole instability. Applying a transverse magnetic field suppresses the keyhole instability by driving a secondary thermoelectric magnetohydrodynamics (TEMHD) flow that alters the net flow vortex. This minimizes protrusions and large-amplitude keyhole oscillations. The suppression effectiveness depends on the laser scanning direction relative to the magnetic field orientation because this controls the Seebeck effect-induced Lorentz force's direction. We show that at LPBF length scales, electromagnetic damping is weak, and for alloys with a large Seebeck coefficient, TEMHD becomes the dominant mechanism controlling flow behind the keyhole.
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