Mechanism of Porosity Mitigation in Aluminum Alloy Additively Manufactured by Galvanometer Scanning Laser Hybrid Double Pulsed-CMT

doi:10.3901/JME.2025.12.093

Abstract

Abstract: The galvanometer scanning laser hybrid double-pulsed cold metal transfer(GSL-D-CMT) additive manufacturing technique has a unique advantage of porosity mitigation and surface quality improvement, and has an important potential application in aerospace, nuclear power field. However, its mechanism for inhibiting pore defects is still unclear, which directly impacts the engineering application of the GSL-D-CMT process in the manufacturing of high-performance aluminum alloy components. To this end, the effects of laser power factor and laser-wire distance on the dynamic evolution, temperature field distribution and porosity formation of molten pool were studied, and the causes of hydrogen pores and keyhole pores and the mechanism of controlling laser parameters to mitigate the porosity defects were revealed in detail. The results indicate that dense pores in aluminum alloy components fabricated by the backward wire WAAM process can be eliminated through coupled galvanometer scanning laser. In this coupled manufacturing process, the porosity exhibits a trend of first decreasing and then increasing as the laser power factor and the laser-wire distance increase. When the laser power factor is 30%, the porosity reaches a minimum of 0.01%. At a laser-wire distance of 5 mm, the porosity is almost 0. The mechanism of GSL-D-CMT inhibiting the porosities lies in the enhanced molten pool convection induced by beam oscillation and double-pulse current, providing favorable kinetic conditions for the shallow keyhole to capture and merge micro-sized pores at the bottom of the molten pool. A wider laser-wire distance results in a more uniform temperature field distribution within the molten pool, reduced temperature gradients, and a slower solidification rate. This broadens the mechanical boundary conditions for stable keyhole evolution and creates favorable thermodynamic conditions for the escape of micro-pores within the molten pool and the capture of larger pores by the keyhole.

Key words: aluminum alloy, galvanometer scanning laser, double pulsed-CMT, additive manufacturing, porosity defects

CLC Number:

TG444

ZHANG Gang, MENG Xu, ZHU Ming, SHI Yu, FAN Ding. Mechanism of Porosity Mitigation in Aluminum Alloy Additively Manufactured by Galvanometer Scanning Laser Hybrid Double Pulsed-CMT[J]. Journal of Mechanical Engineering, 2025, 61(12): 93-103.

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