## 3 Results
### Macroscopical Features of the Island Scan Modeled Specim  
As a consequence of applying six different scan strategies, the surface topography of the Island scan modeled specimen (Figure 4a) shows no clear direction of deformation patterns, as in previous cases. Nevertheless, similar to the island scan stripes specimen in Figure 3a, a pattern of peaks and valleys reflecting the periodicity of the islands is observed. As compared to Figure 3a, an irregular shape of the island topographies is observed, which is caused by combining the different scan strategies in the islands with the order of scanning of the islands, leading to different deformations and edge-effects in the individual islands as well as different locations and extents of the melt-pool digging [24]. Islands with near-circular topographical shapes can be recognized in Figure 4a. They are clearest for the highest and lowest islands as reflected by the circular white rings and the blue circles, and developed because scanning followed either an (1) out-in spiral or (2) in-out spiral scan type, as described by [PERSON] et al. [18].  
Porosity for the island scan modeled specimen is shown in Figure 4b,\(c\). In general, a high content of spherical porosities is observed. Lack-of-fusion defects appear less pronounced than for the island scan stripes in Figure 3, implying that the islands are fused better together. This is confirmed by Figure 4e-g. Most islands are completely fused, while some have a relatively high degree of spherical porosities or lack-of-fusion defects (Figure 4b,_c_). Again, lines of spherical porosities distributed along the y-direction are present, located at or close to the island borders along the x-direction (Figure 4g). However, this time they do not extend through the full length of the specimen, due to the use of the variation in scan strategy. Instead, high concentrations of spherical porosities are observed inside many islands; several islands show depressions (appearing blue in Figure 4a), combined with few spherical porosities. Some of these have developed into funnel-like defects, for example the large yellow pore in Figure 4c. These deep defects are observed in islands that were filled in after their surrounding islands were completed (see Figure S1, where island 354 is where the yellow pore in Figure 4c was created).  
Figure 4: Island scan modeled specimen: **(a)** IFM image showing the surface texture; 3D rendering of the internal porosities identified in Avizo from 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 micrographs and **(g)** degree of porosity as function of x- and y-layer, as calculated in Matlab from CT scan data. High resolution image of **(e,f)** are provided in Figure S5.  
The pore distributions in Figure 4g show that periodic behavior with a periodicity reflecting the island width occurs in the x-direction, albeit less pronounced as in Figure 3g, because of the use of different scan strategies within the islands. Consistently, the heights of the peaks are significantly lower than in Figure 3g, due to fewer lack-of-fusion defects. The periodic behavior in the y-direction (Figure 4g) is also less pronounced than in Figure 3g. An explanation for the occurrence of a pattern in the porosity distribution in both the x- and y-direction, despite the use of different scan strategies, is that the direction of scan types 3-6 are still parallel to the x-direction, implying that lack-of-fusion defects could still occur, albeit less pronounced than in the island scanning stripes specimen. Secondly, it appears that the use of different scan strategies is not sufficient to avoid overlap between islands; even though the frequency of lack-of-fusion defects is reduced, more trapped-gas porosities appear at the borders.