Influence of layer thickness on formation quality, microstructure, mechanical properties, and corrosion resistance of WE43 magnesium alloy fabricated by laser powder bed fusion

Laser powder bed fusion (L-PBF) of Mg alloys has provided tremendous opportunities for customized production of aeronautical and medical parts. Layer thickness (LT) is of great significance to the L-PBF process but has not been studied for Mg alloys. In this study, WE43 Mg alloy bulk cubes, porous scaffolds, and thin walls with layer thicknesses of 10, 20, 30, and 40 μm were fabricated. The required laser energy input increased with increasing layer thickness and was different for the bulk cubes and porous scaffolds. Porosity tended to occur at the connection joints in porous scaffolds for LT40 and could be eliminated by reducing the laser energy input. For thin wall parts, a large overhang angle or a small wall thickness resulted in porosity when a large layer thicknesses was used, and the porosity disappeared by reducing the layer thickness or laser energy input. A deeper keyhole penetration was found in all occasions with porosity, explaining the influence of layer thickness, geometrical structure, and laser energy input on the porosity. All the samples achieved a high fusion quality with a relative density of over 99.5% using the optimized laser energy input. The increased layer thickness resulted to more precipitation phases, finer grain sizes and decreased grain texture. With the similar high fusion quality, the tensile strength and elongation of bulk samples were significantly improved from 257 MPa and 1.41% with the 10 μm layer to 287 MPa and 15.12 % with the 40 μm layer, in accordance with the microstructural change. The effect of layer thickness on the compressive properties of porous scaffolds was limited, however. The corrosion rate of bulk samples accelerated with increasing the layer thickness, mainly attributed to the increased number of precipitation phases.