%P 864-869
%O This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions.
%D 2025
%V 387
%N 6736
%C United States
%L discovery10205876
%I American Association for the Advancement of Science (AAAS)
%X 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.
%J Science
%T Magnetic modulation of keyhole instability during laser welding and additive manufacturing
%A Xianqiang Fan
%A Tristan G Fleming
%A Samuel J Clark
%A Kamel Fezzaa
%A Anna CM Getley
%A Sebastian Marussi
%A Hongze Wang
%A Chu Lun Alex Leung
%A Andrew Kao
%A Peter D Lee