Laser Surface Melting of Cold Metal Transfer Wire Arc Directed Energy Deposited AZ31 Mg Alloy

Abstract

The deposition of Mg alloy using an additive manufacturing process is challenging due to its volatile nature at high temperatures and difficult handling of Mg powder during fabrication. Therefore, the cold metal transfer wire arc additive manufacturing (CMT-WAAM) process deposits AZ31 Mg alloy because of its tremendous potential to fabricate heat-sensitive materials due to comparatively low heat input and wire as a feed material. However, the mechanical properties of CMT-WAAMed AZ31 Mg alloy are still poor due to pores, microcracks, and poor surface finish. Therefore, deposited components cannot be directly used in the application. Machining is required to make the surface smooth and flat before application. However, microcracks and burrs are the primary issues during milling operation, further reducing the mechanical properties and corrosion performance of deposited parts. Therefore, this study uses the laser surface melting (LSM) process to enhance surface properties by minimizing the microcracks and other CMT-WAAMed AZ31 Mg alloy defects. The obtained results of the 3D profilometer show that the surface roughness (R<inf>a</inf>) of machined samples was 3.34 μm, which is reduced to 2.279 μm after laser surface melting treatment. In addition, optical microscope (OM) results exhibited a huge reduction of grain refinement after LSM from 45 ± 3 μm to less than 1 μm with dendrites microstructure. Consequently, the hardness of the surface increased from 60 ± 2 to 143 ± 10 HV due to grain refinement and the formation of secondary phase particles. The grain refinement and uniform distribution of secondary phase particles act as a barrier to Cl−1 corrosive ions, enhancing corrosion resistance after the SLM process. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.