## 5 Conclusions  
Three SLM specimens fabricated with different scanning strategies were investigated and compared with regards to surface texture, porosity, and microstructure. An optimized cellular scanning strategy (island scan modeled) was compared to a simple cellular scanning strategy (island scan stripes) and the basic antiparallel line scanning strategy (line scan). \begin{table}
\begin{tabular}{c c} \hline
**Specimen Designation** & **Avg. Hardness (HV\({}_{0.01}\))** \\ \hline Line Scan & \(474\pm 41\) \\ Island Scan Stripes & \(492\pm 33\) \\ Island Scan Random & \(496\pm 29\) \\ \hline \end{tabular}
\end{table} 
Table 3: Average micro hardness (\(\pm\sigma\)) of SLM specimens according to scan strategy. The surface roughness was lowest for the line scan specimen, but unevenly distributed, and while it increased with the use of island scanning, the texture was more even. However, due to the consistent scan strategy for the island scan stripes, the surface texture had a directional pattern, which was less pronounced in the island scan modeled specimen. Similarly, a low amount of porosity was found in the line scan specimen (0.4%), mainly consisting of spherical pores, while 1.4% and 0.8% was found in the island scan stripes and modeled specimens, respectively. For the island scan stripes, specimen porosity was mainly caused by lack of fusion. The modeled strategy reduced porosity as compared to the stripes strategy and resulted in a significant reduction in lack of fusion porosity, leaving spherical pores as the main porosity type. The work showed how scan strategy affects the microstructure, with regards to the direction of the elongated prior \(\beta\) grains, the martensite morphology, and decomposition into lamellar \(\alpha\)/\(\beta\). In the island scan specimen, the elongated prior \(\beta\) grains were tilted towards the print direction (y-axis), due to the lack of rotation between the layers. Decomposition of the \(\alpha^{\prime}\) martensite into lamellar \(\alpha\)/\(\beta\) was observed in the bottom of the line scan specimen, but not in the island scan specimens. This led to a lower average hardness in the line scan specimen as compared to the island scan specimen (474 HV\({}_{0.01}\) vs. \(\sim\)494 HV\({}_{0.01}\)). In the island scan modeled specimen, the prior \(\beta\) grains were irregular and the martensite morphology was inhomogeneous, clearly indicating different local thermal histories within the specimen, due to combining different local scan strategies. All observations indicate that the thermal histories in the three specimens are affected by the scan strategy and determine the microstructure. However, due to the large amount of porosities in the island scan specimens, it is unclear whether the difference in the thermal history is entirely caused by a difference in scan strategy or also from the geometry change, caused by the large porosities. The following are available online at [[http://www.mdpi.com/2076-3417/9/24/5554/s1](http://www.mdpi.com/2076-3417/9/24/5554/s1)]([http://www.mdpi.com/2076-3417/9/24/5554/s1](http://www.mdpi.com/2076-3417/9/24/5554/s1)), Figure S1: Scanning strategy for the island scan modeled specimen, Figure S2: Scanning sequence for the island scan specimens, Figure S3: Macrographs of line scan specimen: (**a**) sketch of specimen with placement of cuts for the (**b,c**) optical macrographs, Figure S4: Macrographs of island scan stripes specimen: (**a**) sketch of specimen with placement of cuts for the (**b,c**) optical macrographs, Figure S5: Macrographs of island scan modeled specimen: (**a**) sketch of specimen with placement of cuts for the (**b,c**) optical macrographs. [PERSON], [PERSON], [PERSON], and [PERSON]. (all authors) conceived/designed the experiments and analyzed the data; [PERSON] and [PERSON] performed the experiments; [PERSON] prepared the original draft. All authors thoroughly reviewed and edited the manuscript. This research received no external funding.