## 3 Results and Discussion
### Temperature Analysis  
Figure 6 shows the temperature distribution cloud diagram of the laser scanning of the powder support zone and the solid support zone. Figure 6a,b show the difference between the solid support zone and the powder support zone on the X-Y plane, while Figure 6c,d show the difference between the solid support zone and the powder support zone on the Y-Z plane. The cloud images were taken on the same scale, and the temperature scale of the cloud image was processed. A temperature boundary of 570 \({}^{\circ}\)C, which is the melting point of AlSi10 Mg, was added. Therefore, the size of the molten pool in the printing process was within the boundary. In Figure 6c,d, it can be clearly seen that the molten pool in the solid support zone is smaller than the molten pool in the powder support zone. It is hard for heat to travel downward in the powder support zone during the forming process of the overhang structure because the thermal conductivity of powder is much smaller; therefore, the molten pool in the powder support zone is larger [10]. Figure 4: Partial enlargement diagram of the sample. Figure 5: Experiment results: (**a**) deformation and (**b**) formed length of overhang structure. Temperature is the key factor affecting the size of the molten pool. In order to further study the specific process of change of the temperature in different support areas, six points were equally spaced on the first track of both the first and third layers, as shown in Figure 7a,b. On the second and fourth layers, the midpoint of each laser was taken as the research point. In Figure 7, the blue dots represent the secant lines of the overhanging area. The left side of the line is the powder support zone, and the other side is the solid support zone. The interval between the six points in the first layer and the third layer was 0.09 mm, the distance between point A and the starting point of Track 1 on Layer 1 was 0.02 mm, and the distance between point P and the end point of Track 1 on Layer 3 was 0.02 mm. In the second and fourth layers, the midpoints of each scanning track were selected. The spacing of all scanning tracks was 0.13 mm. Figure 8 shows the temperature variation with time at each research point in the first four layers. The pink dotted line in the vertical direction corresponds to the time at which the laser reached this point. As can be seen from Figure 8, the peak temperature appeared after the arrival time. This is because when the laser passes the current point it continues to heat the parts, and the temperature is conducted to the previous point due to heat conduction; therefore, the temperature rises at the previous point and reaches the maximum value. Figure 6: The temperature distribution of layer 1: (**a**) scan of the solid support zone on the X–Y plane; (**b**) scan of the powder support zone on the X–Y plane; (**c**) scan of the solid support zone on the Y–Z plane; and (**d**) scan of the powder support zone on the Y–Z plane. Figure 7: Studied points on different overhang layers: (**a**) Layer 1; (**b**) Layer 2; (**c**) Layer 3; and (**d**) Layer 4. Figure 8a shows the scanning results of the first layer. When the laser scanning was on the solid support zone, the highest temperature at three points, A, B, and C, gradually increased. When the laser scanning was on the powder support zone, the temperature variation range between two points, C and D, was significantly larger than the temperature variation between three points, A, B, and C. When the laser scanning was at point D, the maximum temperature of the point increased significantly, and the increase between two points, C and D, was more than 14%. Figure 8b shows the scanning results of the second layer, which starts from the powder support zone. Figure 8b shows that when the laser scanned from H to I, the maximum temperature decreased significantly, and the temperature between the two points in the same zone kept increasing, such as at G and H and at I and J.