## 3 Results  
### Macroscopical Features of the Line Scan Specim  
A collage of the macroscopic features of the line scan specimen, including surface topography, porosity analysis, and macrographs of x-z and y-z cross sections, is given in Figure 2. Generally, the specimen is higher along the edges, apart from the last scanned side at the top (Figure 2a). The macrographs in Figure 2d-f show that the higher edge along the scan direction is related to distortion of the first scanned corner (to the left). The increased height along the edges in the print direction (y-axis) is not due to deformation, but caused by material build-up (i.e., an edge-effect) as identified in the macrograph in Figure 2e. The build-up happens when a scan line is adjacent to the specimen's border, where the melt pool is surrounded by powder on 3-4 sides as compared to 2 sides for scan lines inside the specimen. The lower thermal conductivity and lower density of the powder relative to solidified material lead to a shape change of the melt pool, which leads to incorporation of more of the residing powder, hereby increasing the melt pool size [23]. In addition, the first melt in the powder sinks down into the powder, leading to an inclined solidified deposit [24], similar to that observed to the left in Figure 2f. The height increase at the edges decreases slightly along the print direction (y-axis). Similarly, the height increase along the scan direction (x-axis) is most pronounced in the corners. Contour scans during fabrication of the specimens can decrease the deformation, but were not applied, because they can lead to even higher edges [23]. Focusing on the specimen surface away from the edges, a green-colored valley is observed over about the first fifth in the print direction, while the remaining surface is uniform in height. The (antiparallel) stripes can be recognized parallel to the x-direction in the surface topography. Computed tomography (CT) results are shown in Figure 2b,c. In order to exclude the surface defects and focus on internal pores, data treatment was performed on a cropped area; see measures in Figure 2b,c. The identified porosities are visualized by 3D renderings in Figure 2b (LFOV) and 2c (4\(\times\) zoom). It is noted that 3D projections of pores give an exaggerated impression of the degree of porosity. The pores are mainly spherical and vary in size. Some pores are aligned along the x-direction, positioning them along the scan lines during the SLM process (Figure 2c, top surface view). The pores are unevenly distributed over the specimen: enhanced pore densities are observed along the edges in the y-direction and in the \"green valley\" observed in Figure 2a. The trend is quantified in Figure 2g, showing the pore distribution as a function of x- and y-directions in the cropped area of the line scan  
Figure 2: Line scan specimen: **(a)** Infinite Focus Microscope (IFM) image showing the surface topography; three-dimensional (3D) rendering of the porosities identified in Avizo from computed tomography (CT) scans of **(b)** full specimen and **(c)** reduced area using 4\(\times\) objective; **(d)** sketch of specimen with placement of cuts for the **(e,f)** optical macrographs and **(g)** amount of porosity as function of x- and y-layer, as calculated in Matlab from CT scan data. High resolution image of **(e,f)** is provided in Figure S3. specimen. In the x-direction (i.e., integrated over the y- and z-direction of the specimen), in addition to the obvious high pore density near the edges, the inserted graph shows an increased number of pores over a distance of 3 mm in the center of the specimen (from 3 to 6 mm). In the y-direction (i.e., integrated over the x- and z-direction of the specimen) the higher density of pores in the \"green valley\" is very distinct. In general, no trend in porosity along the build direction (z-direction) is observed.