## 3 Results and Discussion
### Mechanical Properties  
The results of the tensile experiment on different L-PBF samples are shown in Figure 9. The results show that under the combination of the general scanning strategy and the angle-offset scanning strategy, the tensile properties of the CHESS scanning strategy combination were the highest. Among them, the CHESS&45\({}^{\circ}\) specimen had the best tensile properties, with a tensile strength of 1125 MPa, a yield strength of 912 MPa, and an elongation of 8.2%; the tensile properties of the LINE scanning strategy combination specimen were the lowest, in which the tensile strength of the LINE&90\({}^{\circ}\) specimen was only 810 MPa. Overall, the tensile properties of the samples combined with the CHESS scanning strategy were the best, and the tensile strengths were all higher than 900 MPa, as shown in Figure 9a. From the general scanning strategy, the CHESS scanning strategy had the best tensile performance,  
Figure 8: Surface hardness of L-PBF samples under different combinations of scanning strategies and a single scanning strategy. (**a**) Surface hardness of samples under different combinations of scanning strategies; (**b**) surface hardness of samples under angled offset scanning strategy; (**c**) surface hardness of samples under general scanning strategy. reaching a tensile strength of 1003 MPa, as shown in Figure 9c. From the angle-offset scanning strategy, the 45\({}^{\circ}\) scanning strategy had the best tensile performance, reaching a tensile strength of 715 MPa, as shown in Figure 9b. The performance of the CHESS&45\({}^{\circ}\) scanning strategy combined specimen was greater than that of the single scanning strategy specimen. Compared with the CHESS scanning strategy and the 45\({}^{\circ}\) scanning strategy, the tensile performance of the samples under the CHESS&45\({}^{\circ}\) scanning strategy was improved by 12.8% and 57.3%, respectively. Compared with the research of other scholars, the comprehensive performance of this test sample is better, as shown in Table 4.  
To further explore the tensile conditions of the L-PBF samples under different combinations of scanning strategies and single scanning strategies, the fractures of the tensile samples were analyzed, as shown in Figure 10. The results show that the samples combined with the CHESS scanning strategy were mainly ductile fractures, with a certain amount of dimple structure and step-like slip separation, which was also the reason for the higher elongation of the C0 specimen, as shown in Figure 10a. The fractures of the C45 and C90 samples were mainly ductile fractures, with many dimple structures. Compared with C90 samples, the dimple structure of C45 samples was more obvious, so the tensile strength and elongation of C45 samples were higher, as shown in Figure 10b,c. From the single scanning strategy aspect, the CHESS strategy also had the phenomenon of slip separation, which explained the higher elongation of the CHESS strategy samples, as shown in Figure 10d. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**References**} & **Manufacturing** & **Yield Strength** & \multicolumn{2}{c}{**Ultimate**} & \multirow{2}{*}{**Elongation (\%)**} \\  & **Means** & **(MPa)** & & **(MPa)** \\ \hline
[40] & As fabricated & 937 & 1107 & 7.3 \\
[41] & As fabricated & - & 1188 & 9.5 \\
[42] & As fabricated & 969 & 1087 & 11.3 \\
[43] & As fabricated & 1021 & 1200 & 2.23 \\
[44] & As fabricated & 968 & 1013 & 3.2 \\ In this research & As fabricated & 912 & 1125 & 8.2 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Some other experimental studies on the tensile properties of L-PBF-formed TC4 titanium alloy specimens. Figure 9: Tensile properties of L-PBF samples under different combinations of scanning strategies and a single scanning strategy. (**a**) Tensile properties of L-PBF samples under various combinations of scanning strategies; (**b**) tensile properties of L-PBF samples under angled offset scanning strategy; (**c**) tensile properties of L-PBF samples under general scanning strategy.