## 3 Results and Discussion  
In this part, we investigate the surface modification of the Ti-6 Al-4V (Ti-64) alloy and characterize the resultant surface morphology changes using SEM. Figure 1 shows the surface morphology of the original Ti-64 surface and those subjected to low-temperature immersion corrosion in HF solutions of varying concentrations. The original Ti-64 surface (Figure 1a) exhibited an extremely smooth topography, consistent with the effects of mechanical polishing. While this smooth surface may be advantageous for certain applications, it might not be optimal for osseetiongration in biomedical implants [72]. After low-temperature (5 \({}^{\circ}\)C) immersion corrosion in 3 M HF solution (Figure 1b,c), the Ti-64 surface developed an irregular porous structure. This structural characteristic likely resulted from a selective corrosion process, where certain grains or phases were preferentially dissolved. At lower magnification (Figure 1b), uniform corrosion was observed over a large area, while higher magnification (Figure 1c) revealed more intricate surface features, including micropores and protrusions. The use of 12 M HF solution for low-temperature immersion corrosion (Figure 1d) led to more pronounced surface alterations. The surface exhibited deeper and wider etch pits, accompanied by a more complex three-dimensional network structure. This morphology likely originated from more intense corrosion processes, resulting in substantial material dissolution and redeposition. These surface modification treatments significantly increased the surface roughness and specific surface area of Ti-64, which may enhance cell adhesion and osseetiongration. In particular, the surface structure resulting from the 12 M HF treatment, with its complex three-dimensional topography, may provide a more favorable environment for osteoblast attachment and growth [8; 60]. The observed changes in surface morphology suggest that HF-based low-temperature immersion corrosion is an effective method for modifying Ti-64 surfaces. The ability to control the degree of surface modification by adjusting HF concentration offers potential for tailoring implant surfaces to specific biomedical applications. Further studies are warranted to quantify the relationship between surface treatment parameters and the resulting surface properties, as well as to evaluate the biological response to these modified surfaces in vitro and in vivo. Figure 1: SEM images of Ti-6 Al-4V surfaces. (**a**) As-polished surface, showing smooth morphology. (**b**) Low-magnification (\(\times\)2000) and (**c**) high-magnification (\(\times\)5000) images of surface treated with 3 M HF at 5 \({}^{\circ}\)C, revealing porous structure. (**d**) Surface treated with 12 M HF at 5 \({}^{\circ}\)C, demonstrating more pronounced etching features and complex 3D network structure. Figure 2 illustrates the surface morphology of the Ti-64 alloy after sandblasting treatment at a 45\({}^{\circ}\) angle using zirconia sand of different grit sizes (80 and 120 grit). This surface modification technique aims to increase surface roughness, thereby enhancing biocompatibility and osseointegration potential. As evident from Figure 2a,b, the sandblasting treatment significantly altered the Ti-64 surface. Both grit sizes resulted in the formation of complex three-dimensional structures, characterized by irregular protrusions and fissures. This surface morphology can be attributed to the continuous impact and shear forces exerted by high-velocity zirconia particles on the material surface. Comparing Figure 2a,b, we observe that treatment with 80-grit sand (Figure 2a) produced larger pits and more pronounced plastic deformation features. This may be due to the higher impact energy of larger sand particles, resulting in more extensive surface deformation. In contrast, treatment with 120-grit sand (Figure 2b) yielded a finer and more uniform texture, which may be advantageous for subsequent cell adhesion and proliferation [10,40].