Structural and Mechanical Property Evolution During the Processing of Semi-Finished Products from Ti-xNb-4Zi-1Si Biomedical Alloys (x = 12 and 18 wt.%)

Biomedical Ti–Nb–Zr–Si alloys containing 12 and 18 wt.% Nb were fabricated by electron beam melting and subjected to thermomechanical processing, including forging, cross-helical rolling, and subsequent cooling or quenching. The effects of Nb content and processing route on phase composition, microstructure, and mechanical properties were systematically investigated using X-ray diffraction, scanning electron microscopy, and tensile testing. The results indicate that increasing Nb content promotes stabilization of the metastable α″ phase, leading to a significant reduction in elastic modulus. The Ti–18Nb–4Zr–1Si alloy exhibited a modulus of ~60 GPa after rolling, which further decreased to ~40 GPa after additional quenching. In contrast, the Ti–12Nb–4Zr–1Si alloy showed higher values of 76–94 GPa due to the predominance of the α′ phase. Both alloys demonstrated a favorable combination of strength and ductility. Microstructural analysis revealed the formation of silicides, whose type and morphology depend on Nb content and processing conditions. The Ti–12Nb–4Zr–1Si alloy predominantly contains (Ti,Zr)5Si3, whereas the Ti–18Nb–4Zr–1Si alloy exhibits complex silicides composed of (Ti,Zr)5Si3 and (Ti,Zr)3Si phases. These results highlight the potential of controlling phase composition and silicide evolution to tailor mechanical properties, particularly the elastic modulus, for biomedical applications.