# Multi-Objective Optimization Study on Production of AlSi10 Mg Alloy by Laser Powder Bed Fusion
## 3 Results and Discussions  
Data obtained from experimental combinations were analyzed with a full factorial experimental design in the Minitab V20 program. This design was applied to investigate the effects of laser power, hatch distance, and scan speed on surface roughness and relative density, and the results were evaluated with an ANOVA. The average main effect plots obtained for surface roughness and relative density are shown in Figures 4 and 5, respectively. In the production of the AlSi10 Mg alloy by the SLM method, parameters such as laser power, hatch distance, laser diameter, and scan speed cause significant changes in Ra values [4]. When Figure 4 is examined, it is seen that the surface roughness decreases with the increase in laser power. This result is consistent with the literature [4; 6; 16]. Surface roughness increases with increasing scan speed [17]. It is thought that this is due to insufficient time for the powder material to melt [6]. The increase in the hatch distance caused a decrease in surface roughness. In the study of [PERSON] et al., it was observed that the surface roughness decreased as the hatch distance increased from 0.10 mm to 0.13 mm, and the lowest roughness was obtained at a distance of 0.13 mm [4]. Figure 4: Surface roughness main effect plot. In Figure 5, when the laser power is increased between 200 W and 275 W, the relative density of the samples increases. In the studies of [PERSON] and [PERSON], it is stated that the laser power was used in the range of 200-280 W. Increasing the laser power between 240 and 280 W resulted in a faster relative density increase compared to the increase in the range of 200 and 240 W. It is stated that the relative density increases because the high laser power provides the energy required to melt the powder bed properly [18]. [PERSON] et al. explain that the increase in laser power increases the amount of energy received by the powder, improves the fluidity of the powder during the melting process, and causes the internal voids to decrease and the relative density to increase. They also state that if the laser power is too high, the powder receives excessive energy and causes it to burn or vaporize, and this process causes the formation of internal voids and the relative density to decrease [19]. According to the graph, the increase in the hatch distance leads to a decrease in the relative density. A similar situation was observed in the studies of [PERSON] et al. [20]. [PERSON] states that wider scan intervals reduce the overlap between layers, and as a result, unmelted powder accumulates and causes voids to form. It is stated that these voids reduce the relative density [21]. When the scan speed was increased from 800 mm/s to 1400 mm/s, the relative density of the sample decreased. According to [PERSON] et al., this decreasing trend is due to the fact that high scan speeds cause the accumulation of unmelted particles during the solidification phase and an increase in the balling phenomenon [22]. A Pareto graph of the standardized effects of laser power, hatch distance and scan speed and the interaction results of these factors on surface roughness and relative density is given in Figure 6.  
In the Pareto graph given in Figure 6, laser power (LP), scan speed (SS), and the interactions of these two factors show significant results on the surface roughness. On the other hand, hatch distance (HD) remained below the Pareto line (12.71) and did not show a significant effect on the surface roughness. In terms of relative density, laser power (LP), hatch distance (HD), scan speed (SS), and the interactions of these factors remained below the Pareto line and did not have a significant effect on the relative density. Figure 5: Relative density main effect plot. and it successfully explains the surface roughness.