Grain refinement through severe plastic deformation is a promising strategy to simultaneously tune the mechanical and surface properties of biomedical titanium alloys. High-Pressure Sliding (HPS) was applied to Ti-6Al-7Nb alloys plate with a thickness of 1 mm at 3 GPa with sliding distances of 5, 10, 15, and 20 mm, and a non-processed specimen served as the control. Microstructural evolution was characterized by X-ray diffraction and transmission electron microscopy. Additionally and tensile tests were performed to evaluate the mechanical properties. The biological responses of MC3T3-E1 mouse pre-osteoblasts cultured on the microstructurally refined specimens were examined in vitro. Cell attachment morphology was evaluated by immunofluorescence staining, while cell proliferation and early osteogenic differentiation were quantified using a WST-8 assay and real-time RT-PCR.
HPS processing under 3 GPa induced the evolution of an ultrafine-grained microstructure from the initial coarse-grained state, while suppressing phase transformation. The development of a preferred grain orientation was observed with increasing sliding distance. This structural evolution, combined with the UFG formation, led to enhanced mechanical properties, achieving high strength and hardness while retaining favorable total elongation.
The HPS-processed specimens also induced elongated cell morphology and polarized focal adhesion distribution compared with the control. Furthermore, enhanced proliferation and upregulated expression of early osteogenic genes, such as RUNX2, COL1alpha, and Akp2, were observed during early differentiation.
These findings demonstrate that HPS-processed Ti-6Al-7Nb with ultrafine grains achieves a favorable combination of high hardness, high tensile strength, and adequate total elongation, while also promoting osteoblast polarization and osteogenic gene expression. Such microstructurally refined Ti-6Al-7Nb alloys represent promising candidates for high-load biomedical applications, including narrow-diameter dental implants.
