## 3 Results and Discussion
### Microhardness and Microstructure Analysis  
Table 3 gives the experimental outcomes of the measured microhardness (HV). The varying hardness values with the variation in laser power and scanning speed for AlSi12 is depicted in Figure 3. The laser power was discovered to greatly affect the fabricated samples' hardness. The hardness steadily declined from 131 HV to about 97 HV (B1-1 to C1-1) as the laser power reduced from 200 W to 50 W. The maximum hardness value of about 131 HV was observed at a laser power of 200 W and a scanning speed of 1000 mm/s, while the hardness obtained by high-pressure casting was 72 HV (reported by [PERSON] et al. [20]). The processing parameters for Sample D1-1 and D1-2, as shown in Figure 4, could not fabricate any specimen, solely due to the combination of very low laser power and high scanning speed. Figure 5 shows the OM micrographs describing the microstructure of the SLM-fabricated AlSi12 specimen from a laser power of 200 W and scanning speed of 200-1000 mm/s. All samples showed similar micrographs. Figure 5 represents the sample with the maximum hardness of 131.48 HV. The observed microstructures were not uniform throughout the material but exhibited the typical laser tracks of SLM processing also observed by and [PERSON] and [PERSON] (2012) [21] and [PERSON] et al. [22]. The tracks consisted of scale-like morphology, which was also detected by [PERSON] et al. [23]. The cellular and dendrite growth within the grain was also seen in the work by [PERSON] et al. [24], which  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Parameter** & **Units** & & **Levels** & & \\ \hline Scanning speed & mm/s & 200 & 500 & 850 & 1000 \\ Laser power & W & 50 & 100 & 150 & 200 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Range of matrix building parameters.  
they ascribed to the eutectic silicon particles being located at the cellular boundaries. The boundaries in Figure 5 match the portions where two unlike laser tracks overlapped (revealing a hatch overlap), which were hence melted two times. There were some porosities that were observed that may have been caused by the printing parameters. In Figure 5a,b,d, the pores are indicated by the dark areas. It is possible for gases to become trapped in the material when the metal solidifies during fabrication. This may cause the microstructure to develop pores or voids. Thus, porosity may be attributed to the solidification process. No cracks were observed.  
Figure 3: Hardness values of SLM-built AlSi12 alloy.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sample No** & **Material AlSi12** & **LP (W)** & **SS (mm/s)** & **Hardness Value** \\ \hline
1 & A1-1 & 150 & 1000 & 107.32 \\
2 & A1-2 & 150 & 850 & 116.27 \\
3 & A1-3 & 150 & 500 & 110.75 \\
4 & A1-4 & 150 & 200 & 124.40 \\
5 & B1-1 & 200 & 1000 & 131.48 \\
6 & B1-2 & 200 & 850 & 128.82 \\
7 & B1-3 & 200 & 500 & 120.36 \\
8 & B1-4 & 200 & 200 & 121.23 \\
9 & C1-1 & 100 & 1000 & 75.15 \\
10 & C1-2 & 100 & 850 & 103.48 \\
11 & C1-3 & 100 & 500 & 108.70 \\
12 & C1-4 & 100 & 200 & 118.02 \\
13 & D1-1 & 50 & 1000 & - \\
14 & D1-2 & 50 & 850 & - \\
15 & D1-3 & 50 & 500 & 97.66 \\
16 & D1-4 & 50 & 200 & 109.34 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Microhardness values of SLM-built AlSi12 alloy.