## 3 Results and Discussion
### Microstructure  
The microstructures of different L-PBF samples are shown in Figure 12. The results show that the microstructure of the L-PBF samples was mainly the primary \(\beta\) phase and \(\alpha\)' martensite phase. Nevertheless, the composition and distribution had specific differences under different scanning strategies. The microstructure distribution of the CHESS scanning strategy combination sample was uniform, and the melt channel was visible. A certain number of columnar \(\beta\)-crystals were distributed in the longitudinal section, and the grain boundaries were clear and uniformly distributed. From the analysis of the combination of scanning strategies, there were no holes on the upper surface of the C0-C90 sample, the melt channel was clear, and the distribution of each phase was uniform, as shown in Figure 12a-c. However, under the angle-offset scanning strategy, the upper surface of the sample had some holes, and the melt channel was unclear. When the angle offset was 0\({}^{\circ}\), the size of the pores on the surface of the sample was smaller, while when the angle offset was 45\({}^{\circ}\), the size of the pores was larger and accompanied by a certain number of cracks; when the angle offset was 90\({}^{\circ}\), the size of the pores was further increased, and their distribution was paralleled to the offset angle, as shown in Figure 12d-f. The longitudinal microstructure of the sample is shown in Figure 12g-r. It was found that a certain number of columnar \(\beta\) crystals were distributed in the longitudinal section of the C0-C90 sample, which was paralleled to the build direction. In addition, the forming layers were bonded with clear boundaries well, the columnar \(\beta\)-crystals grew continuously, and the grain boundaries were visible, as shown in Figure 12g-i.p-r. Among them, the columnar \(\beta\)-crystal size of the C45 sample was relatively coarse, which enhanced the sample's tensile strength, as shown in Figure 12h. Under the general scanning strategy, the columnar \(\beta\) grain boundaries were unclear. The growth was interrupted; the boundaries between the forming layers were blurred, and there were tiny gaps between the layers, as shown in Figure 12j-l. Some severe delamination occurred in the sample under the angle-offset scanning strategy, which was also the reason for the low density of the piece, as shown in Figure 12m-o. It was found that when the angle offset was 45\({}^{\circ}\) and 90\({}^{\circ}\), the columnar \(\beta\)-crystal growth of the  
Figure 11: The density of L-PBF samples under different combinations of scanning strategies and a single scanning strategy. (**a**) The density of L-PBF samples under various combinations of scanning strategies; (**b**) the density of samples under angular offset scanning and general scanning strategies.  
sample was seriously hindered due to the severe delamination phenomenon. The crystals were laterally staggered, and the growth was interrupted. This led to a decrease in the mechanical properties of the specimen, and the delamination phenomenon also made the specimen surface more uneven, as shown in Figure 12n-o.  
Figure 12: Metallographic structure of L-PBF samples under different combinations of scanning strategies and a single scanning strategy. (**a–f**) Corresponding to the upper-surface metallographic structure of the C0, C45, C90, 0\({}^{\circ}\), 45\({}^{\circ}\), and 90\({}^{\circ}\) samples, respectively; (**g–o**) corresponding to the longitudinal-section metallographic structure of C0, C45, C90, CHESS, STRIPE, LINE, 0\({}^{\circ}\), 45\({}^{\circ}\), and 90\({}^{\circ}\) samples respectively; (**p–r**) SEM images of C0, C45, and C90 samples.