β-type titanium (Ti) alloys have attracted a lot of attention as novel biomedical materials in the past decades due to their low elastic moduli and good biocompatibility. This article provides a broad and extensive review of β-type Ti alloys in terms of alloy design, preparation methods, mechanical properties, corrosion behavior, and biocompatibility. After briefly introducing the development of Ti and Ti alloys for biomedical applications, this article reviews the design of β-type Ti alloys from the perspective of the molybdenum equivalency (Mo_eq) method and DV-Xα molecular orbital method. Based on these methods, a considerable number of β-type Ti alloys are developed. Although β-type Ti alloys have lower elastic moduli compared with other types of Ti alloys, they still possess higher elastic moduli than human bones. Therefore, porous β-type Ti alloys with declined elastic modulus have been developed by some preparation methods, such as powder metallurgy, additive manufacture and so on. As reviewed, β-type Ti alloys have comparable or even better mechanical properties, corrosion behavior, and biocompatibility compared with other types of Ti alloys. Hence, β-type Ti alloys are the more suitable materials used as implant materials. However, there are still some problems with β-type Ti alloys, such as biological inertness. As such, summarizing the findings from the current literature, suggestions forβ-type Ti alloys with bioactive coatings are proposed for the future development.

Implants made of titanium and its alloys are currently widely used in the human body. A series of surface modification methods developed nowadays enable titanium alloy implants to serve effectively in the human body for a long time. This paper reviews three different types of surface modification technologies for biomedical titanium alloys: physical, chemical, and biological, with particular attention to the assistance of these three technologies on the biological properties of titanium alloys. The physical method can change the surface morphology of titanium implants and prepare specific coatings for the implants, such as oxide films, bioactive molecules, drugs, etc. Chemical and biological surface modification technologies can minimize bacterial adhesion on the implant surface, improve the integration of soft tissue around the implant, prevent the occurrence of peri-implantitis, and accelerate the process of damage repair. An ideal titanium implant surface should balance the optimal surface morphology, chemical properties, and bionic characteristics to accelerate bone integration, enhance stability, and reduce peri-implant inflammation. Future research should focus on combining technologies, exploring interactions at the cellular and molecular levels, and conducting extensive in vitro and in vivo studies to verify the effectiveness and safety of modified surfaces. The progress in these fields will help overcome the existing limitations, improve the performance of implants, and obtain better clinical results.

There is limited research on metastable pitting corrosion in an acidic environment, and acid is a major challenge for material corrosion. Therefore, this work investigated the metastable pitting corrosion of laser powder bed fusion (LPBF)-produced Ti–6Al–4V, in Hank’s solution, at different pH values (pH = 3, 5, and 7). This work investigated the effect of acid on the characteristics of passive films, as well as the change in metastable pitting behavior. Based on the results of electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS), the passive film will be inhibited and dissolved under the influence of H⁺. The higher the concentration of H⁺, the thinner the passive film. Potentiodynamic polarization tests reveal that LPBFed Ti–6Al–4V in Hank’s solution, at pH 3, has more obvious metastable pitting corrosion. This is because the higher the H⁺ concentration, the more Cl^- is adsorbed on the surface of the passive film, which is prone to generate soluble chlorides by competitive adsorption with oxygen atoms and thus develop into metastable pitting corrosion.

Ti-35Nb-2Ta-3Zr (TNTZ) β-titanium alloy is attractive for biomedical applications because of its relatively low elastic modulus and composition based on nominally non-cytotoxic alloying elements; however, its surface hardness and intrinsic bioactivity remain limited. In this study, Zn nanoparticles were incorporated into the near-surface region of TNTZ by friction stir processing (FSP), followed by compression plasma flow (CPF) treatment in nitrogen. Cross-sectional scanning electron microscopy and energy-dispersive X-ray spectroscopy, X-ray diffraction, microhardness testing, and inductively coupled plasma mass spectrometry after 60 days of immersion in simulated body fluid were used to characterize the modified layers. CPF treatment produced a distinct surface-modified layer approximately 10–15 μm thick, increased the Zn signal within the upper approximately 11 μm, and generated diffraction peaks assigned to Ti₂N. The fitted β-phase lattice parameter decreased with nominal X-ray penetration depth, and tensile residual stresses were calculated for all CPF-treated conditions. Sample 1 exhibited the highest microhardness at the lowest applied load. After 60 days of immersion, the mean Zn concentration was 261.87 ± 0.0031 μg/L for FSP and 102.41 ± 0.0063 μg/L for FSP + CPF, corresponding to an approximately 60.9% lower mean cumulative Zn concentration after CPF treatment. Electrochemical, tribological, and biological testing is still required to establish corrosion, wear, and biological performance.