Amongst biomedical metallic materials, titanium alloys are normally used as structural permanent implants due to their favourable combination of mechanical properties and biocompatibility. However, commonly implanted titanium alloys are expensive and, unless purposely surface treated, generally cannot prevent surgical infections related to bacteria. Specifically, bacterial infection in biomedical protheses leads to inflammation, obstruction of the healing process, prevention of osteogenesis and, eventually, premature failure of the implant. This work therefore analysis the development of new ternary Ti-based alloys with built-in antibacterial capability as pathogenic bacterial infection occurring during surgery is a raising issue of metallic biomedical implants. The new Ti-based alloys were designed to be manufactured via powder metallurgy, which permits to successfully produce chemically homogeneous materials, key for a uniform antibacterial response, at lower cost. It is found that, primarily due to the stabilisation of the beta phase, the amount of the selected β stabilising alloying elements directly increases the mechanical performance and the antibacterial capability. Consequently, new ternary Ti-based alloys are promising candidates for structural prosthesis functionalised with antibacterial capability.

Ti alloys contemplating the simultaneous addition of Fe and Nb are available in the literature as Fe enhances the strength and Nb improves the biological behaviour of Ti. Nevertheless, casting has been the main manufacturing process, the Nb content is normally ≥10 wt.%, and no tensile properties are available. In this study, Ti-5Fe-xNb alloys (x = 2, 6, and 9 wt.%) were produced via powder metallurgy, which is more energy efficient than casting, with the aim of understanding the relationship between the mechanical behaviour and the microstructural changes brought about by the progressive addition of a greater amount of Nb. This study shows that the increment of the Nb content reduces the densification of the alloys, as the relative density decreases from 98.2% to 95.0%, but remarkably increases the volume fraction of the stabilised β phase (14→36%). Accordingly, the Ti-5Fe-xNb alloys are characterised by Widmanstätten microstructures, which become finer for higher Nb contents, and progressively higher mechanical properties including yield stress (725–949 MPa), ultimate tensile strength (828–995 MPa), and hardness (66.5–67.6 HRA), but lower elongation to fracture (4.0–5.1%). It is found that the ductility is much more influenced by the presence of the residual pores, whereas the strength greatly depends on the microstructural changes brought about by the addition of the alloying elements.

The individual addition of Nb, Fe, or Mn to Ti has been greatly studied, but their combined addition has been much less understood, especially for the Ti-Nb-Mn system. Moreover, the full potential of using powder metallurgy to reduce their manufacturing cost has not been properly exploited and, even though proposed for structural applications, rarely tensile properties were reported. In this study new powder metallurgy Ti-6Nb-x(Fe or Mn) alloys were produced and the correlation between their microstructure and tensile properties established. It was found that, for a similar addition of Nb, Mn is a stronger eutectoid beta stabiliser compared to Fe leading to more refined lamellar structures and a greater amount of stabilised beta phase. Accordingly, higher tensile properties (832-1050 MPa yield stress and 910-1080 MPa ultimate tensile strength) and lower ductility (6.3-1.7 %) were, thus, obtained in ternary Ti-Nb-Mn alloys compared to Ti-Nb-Fe alloys, but the actual stress/strain pairs and hardness are the compromise between the volumetric fraction of residual porosity (3.6-4.9 %), which increases with the amount of alloying elements, and the microstructural changes induced by actual chemical composition.(c) 2022 Elsevier B.V. All rights reserved.

Zirconium is an ideal alloying element to be added to titanium for biomedical applications due to its non-toxic behaviour and high solubility. In literature, binary Ti–Zr alloys have primarily been manufactured via casting, while powder metallurgy has been partly ignored even though of its intrinsic advantages. Moreover, the tensile properties of Ti–Zr alloys, and so their work hardening behaviour, has not been properly understood. Consequently, this study investigated the effects that lean additions of Zr have on the microstructure and properties of powder metallurgy binary Ti–Zr alloys produced by uniaxial pressing plus sintering. It is found that the incremental addition of Zr reduces the compressibility and enhances the densification, resulting in comparable relative density values for different Zr contents. The addition of Zr leads to the formation of a lamellar microstructure, which is progressively refined by further addition of Zr. Therefore, the tensile strength and hardness increase with the incremental addition of Zr, while the ductility initially increases and then decreases. Although the studied Ti–Zr alloys have similar work hardening, their actual behaviour is directly dictated by the microstructural features.

Ti alloys, generally made via wrought metallurgy, are commonly used as biomedical materials. The manufacturing of such alloys via powder metallurgy offers the possibility to reduce the cost as well as to develop innovative compositions not otherwise achievable. The aim of this study is to understand the effect that the progressive addition of Al has on the physical and mechanical behaviour of the low-cost powder metallurgy Ti-5Fe alloy for structural biomedical implants. Specifically, Ti-5Fe-xAl (x = 1-6 w.%) alloys were developed combining blending elemental and cold pressing plus vacuum sintering to further limit the manufacturing costs as Al is lighter and cheaper than Ti. This investigation demonstrates that the amount of Al added significantly changes the thermodynamics of the sintering process and induces microstructural modifications such as grain refinement. These effects jointly with the Al solid solution strengthening leads to progressively stronger and harder (but less ductile) alpha+beta Ti alloys characterised by the typical alpha+beta lamellar microstructure with mechanical behaviour suitable for a variety of structural biomedical implants.