High power laser powder bed fusion of AlSi10Mg alloy: Effect of layer thickness on defect, microstructure and mechanical property

In this paper, high power laser powder bed fusion (HP-LPBF) of AlSi10Mg alloy was conducted under the conventional level layer thickness (0.05 mm) and the sub-millimeter level thickness (0.10–0.25 mm). The effect of layer thickness on defect, microstructure and mechanical property of the HP-LPBF AlSi10Mg alloy are studied. The results first demonstrate that the relative density of the HP-LPBF sample is higher than 99.8% when the layer thickness is 0.05–0.10 mm and decreases monotonously with the layer thickness increasing from 0.05 to 0.25 mm. Then, it is found that all the HP-LPBF samples possess a cellular structure composed of α-Al matrix and eutectic Si. However, the crystallographic features are significantly influenced by the layer thickness. When the layer thickness is only 0.05 mm, the α-Al matrix is mainly composed of columnar grains with <100> orientation parallel to the build direction. With the increase of layer thickness, the growth direction of the columnar grains becomes diversified whilst the proportion of the equiaxed grains increases, resulting in the decrease of <100> texture intensity. Finally, it is shown that the tensile property of the HP-LPBF sample presents a V-shaped relationship with the layer thickness. Except the minimum value which is obtained at the layer thickness of 0.20 mm, the tensile properties of the HP-LPBF samples are superior to that of the die-casting AlSi10Mg. The relevant influence mechanisms are also revealed.