Laser induced keyhole reshaping in laser powder bed fusion of aluminum alloy

Abstract

Conventional powder bed fusion by laser beam (PBF-LB) utilizing high beam energy often generates unstable keyhole dynamics, leading to pore formation and compromised mechanical performance, especially for aluminum alloys. To address this limitation, we propose a novel Laser Keyhole Reshaping technology enhanced PBF-LB (LKRS-PBF-LB) strategy, integrating pulsed and continuous lasers to stabilize keyhole morphology. Experimental and computational analyses reveal that pulsed-laser-induced shockwaves dynamically reverse keyhole wall pressures, expanding the keyhole diameter (43→58 μm) and stabilizing its shape (J→I transition), thereby reducing porosity by an order of magnitude (3.63 %→0.14 %). Keyhole stabilization concurrently suppresses spattering by mitigating vapor pressure fluctuations and lowering peak pressures. Numerical simulations demonstrate enhanced melt flow and attenuated thermal gradients, promoting columnar-to-equiaxed transition and grain refinement. The LKRS-processed samples exhibited simultaneous enhancement in tensile strength (59.6 % increase) and ductility (0.78 %→2 %), attributable to porosity elimination and grain refinement. This approach introduces a novel keyhole reshaping technique that mitigates intrinsic instability, thereby enabling new avenues for advanced additive manufacturing with enhanced performance.