ReviewTitanium alloys in total joint replacement—a materials science perspective
Abstract
Increased use of titanium alloys as biomaterials is occurring due to their lower modulus, superior biocompatibility and enhanced corrosion resistance when compared to more conventional stainless steels and cobalt-based alloys. These attractive properties were a driving force for the early introduction of α (cpTi) and α+β (Ti–6Al–4V) alloys as well as for the more recent development of new Ti-alloy compositions and orthopaedic metastable β titanium alloys. The later possess enhanced biocompatibility, reduced elastic modulus, and superior strain-controlled and notch fatigue resistance. However, the poor shear strength and wear resistance of titanium alloys have nevertheless limited their biomedical use. Although the wear resistance of β-Ti alloys has shown some improvement when compared to α+β alloys, the ultimate utility of orthopaedic titanium alloys as wear components will require a more complete fundamental understanding of the wear mechanisms involved. This review examines current information on the physical and mechanical characteristics of titanium alloys used in artifical joint replacement prostheses, with a special focus on those issues associated with the long-term prosthetic requirements, e.g., fatigue and wear.
References (0)
Cited by (3151)
Improvement of micro/nano-structure and corrosion resistance of TiCu alloy by addition of tin and their Sr-hydroxyapatite coating
2024, Journal of Alloys and CompoundsThis study explores the influence of tin (Sn) content on the properties of Ti7CuXSn (X = 2, 7, and 15 wt%) alloys, in both as-cast and heat-treated conditions. The investigation reveals that an elevated Sn content within the Ti7Cu alloy results in the formation of finer grain structures. Rapid quenching processes lead to the development of an ultrafine martensitic structure and the formation of (Ti,Sn)2Cu intermetallic compounds within the Ti7CuXSn alloys. Subsequent heat treatment processes induce the transformation of the ultrafine martensitic structure into a coarser one, accompanied by an increase in the volume fraction of (Ti,Sn)2Cu. X-ray diffraction (XRD) analysis validates the presence of α/α'-Ti(Sn,Cu) phases and (Ti,Sn)2Cu intermetallics across all alloy compositions. The Ti7Cu15Sn alloy demonstrates higher microhardness, primarily attributed to its smaller grain size, reduced lamellar spacing, and increased volume fraction of (Ti,Sn)2Cu. Furthermore, all specimens exhibit heightened microhardness following heat treatment due to the martensitic structure with heterogeneous and homogeneous nucleation of (Ti,Sn)2Cu intermediate growth. Electrochemical analysis reveals an enhanced corrosion resistance in the Ti7Cu15Sn alloy, attributed to its elevated Sn content. Nonetheless, the as-cast Ti7Cu15Sn alloy displays superior corrosion resistance, albeit with a marginal reduction in electrochemical performance following heat treatment. Surface characterization signifies the formation of a uniform oxide film, underscoring commendable corrosion resistance in both as-cast and heat-treated Ti7CuXSn alloys. Additionally, the study investigates the deposition of strontium (Sr)-doped ceramic coatings on as-cast Ti7Cu15Sn alloys. It is demonstrated that higher current density parameters yield denser and more crystalline Sr-HA coatings. Energy dispersive spectroscopy (EDS) mapping confirms the successful incorporation of Sr into the coating, showcasing its potential for applications in the field of biomedicine. Thus, this investigation highlights the significant impact of Sn content on microstructural refinement, enhancements in mechanical properties, and improved electrochemical performance within Ti7CuXSn alloys. These findings offer valuable insights for the design and optimization of alloy performance in diverse applications.
Tailoring thermodynamic stability, mechanical properties, and anisotropies in TiX (X=Nb, Zr) disordered alloys: A first-principles study
2024, Journal of Non-Crystalline SolidsThis paper employs first principles to calculate the elastic modulus and anisotropies of β-TiX (X=Nb/Zr) disordered models. Based on the special quasi-random structures (SQS) theory and utilizing the open-source software ICET, disordered structures of β-TiX (X=Nb/Zr) are established, and their formation energies and the stability of the β phase are determined. Subsequently, the elastic constants of these structures are computed, followed by calculations of the elastic anisotropies of Young's modulus and an analysis of alloys prone to fatigue cracking. The insights provided contribute to a deeper understanding of the mechanical properties of β-TiX alloys, facilitating their design and optimization for various applications.
Effect of density grading on the mechanical behaviour of advanced functionally graded lattice structures
2024, Journal of the Mechanical Behavior of Biomedical MaterialsLattice structures have found significant applications in the biomedical field due to their interesting combination of mechanical and biological properties. Among these, functionally graded structures sparked interest because of their potential of varying their mechanical properties throughout the volume, allowing the design of biomedical devices able to match the characteristics of a graded structure like human bone. The aim of this works is the study of the effect of the density grading on the mechanical response and the failure mechanisms of a novel functionally graded lattice structure, namely Triply Arranged Octagonal Rings (TAOR). The mechanical behaviour was compared with the same lattice structures having constant density ratio. Electron Beam Melting technology was used to manufacture titanium alloy specimens with global relative densities from 10% to 30%. Functionally graded structures were obtained by increasing the relative density along the specimen, by individually designing the lattice's layers. Scanning electron and a digital microscopy were used to evaluate the dimensional mismatch between actual and designed structures. Compressive tests were carried out to obtain the mechanical properties and to evaluate the collapse modes of the structures in relation to their average relative density and lattice grading. Open-source Digital Image Correlation algorithm was applied to evaluate the deformation behaviour of the structures and to calculate their elastic moduli. The results showed that uniform density structures provide higher mechanical properties than functionally graded ones. The Digital Image Correlation results showed the possibility of effectively designing the different layers of functionally graded structures selecting desired local mechanical properties to mimic the different characteristics of cortical and cancellous bone.
Porous functionally graded material based on a new Ti-25Nb-5Zr-(2Sn) alloy produced using the powder metallurgy technique
2024, Journal of Alloys and CompoundsDevelopments in engineering and medicine have allowed patients' health and quality of life to be supported by implants. Unfortunately, widely used titanium-based alloys with aluminum and vanadium are not ideal materials. The first problem is a mechanical mismatch between human bone and the implant material, and the second issue is the presence of Al or V, which are harmful for the human body and health. This article focuses on the holistic design and production of titanium-based materials with vital elements. The zoned, gradient element can exhibit better mechanical properties and improve the connection between the implant and the bone. The samples in two constructions were built with two different zones. The powders for samples were prepared using the powder metallurgy technique with sieve separation. Phillips X-ray X′Pert diffractometer and PDF4 + database performed the phase composition analysis. The Scanning electron microscope allow the samples observation. Stereological methods assessed porosity and PAR M370 Scanning Electrochemical Workstation. The designed technology based on the powder metallurgy method allows for producing functional, two-zoned graded materials with variable porosity. The phase composition analysis confirmed partially synthesis. Additionally, the observation of the microstructure of the sintered samples revealed the presence of two permanently connected zones. Preliminary mechanical research was conducted to evaluate the potential use of the material as an implant material. The proposal to use two-zone construction of components for implants is dictated by the possibility of personalizing implants for patients, taking into account personal characteristics and needs.
Increasing temperature accelerates Ti-6Al-4V oxide degradation and selective dissolution: An Arrhenius-based analysis
2024, Acta BiomaterialiaTi-6Al-4V selective dissolution occurs in vivo on orthopedic implants as the leading edge of a pitting corrosion attack. A gap persists in our fundamental understanding of selective dissolution and pre-clinical tests fail to reproduce this damage. While CoCrMo clinical use decreases, Ti-6Al-4V and the crevice geometries where corrosion can occur remain ubiquitous in implant design. Additionally, most additively manufactured devices cleared by the FDA use Ti-6Al-4V. Accelerated preclinical testing, therefore, would aid in the evaluation of new titanium devices and biomaterials. In this study, using temperature, we (1) developed an accelerated pre-clinical methodology to rapidly induce dissolution and (2) investigated the structure-property relationship between the dissolving surface and the oxide layer. We hypothesized that solution temperature and H2O2 concentration would accelerate oxide degradation, increase corrosion kinetics and decrease experimental times. To assess this effect, we selected temperatures above (45 °C), below (24 °C), and at (37 °C) physiological levels. Then, we acquired electrochemical impedance spectra during active β dissolution, showing significant decreases in oxide polarization resistance (Rp) both over time (p = 0.000) and as temperature increased (p = 0.000). Next, using the impedance response as a guide, we quantified the extent of selective dissolution in scanning electron micrographs. As the temperature increased, the corrosion rate increased in an Arrhenius-dependent manner. Last, we identified three surface classes as the oxide properties changed: undissolved, transition and dissolved. These results indicate a concentration and temperature dependent structure-property relationship between the solution, the protective oxide film, and the substrate alloy. Additionally, we show how supraphysiological temperatures induce structurally similar dissolution to tests run at 37 °C in less experimental time.
Within modular taper junctions of total hip replacement systems, retrieval studies document severe corrosion including Ti-6AL-4V selective dissolution. Current pre-clinical tests and ASTM standards fail to reproduce this damage, preventing accurate screening of titanium-based biomaterials and implant designs. In this study, we induce selective dissolution using accelerated temperatures. Building off previous work, we use electrochemical impedance spectroscopy to rapidly monitor the oxide film during dissolution. We elucidate components of the dissolution mechanism, where oxide degradation precedes pit nucleation within the β phase. Using an Arrhenius approach, we relate these accelerated testing conditions to more physiologically relevant solution concentrations. In total, this study shows the importance of including adverse electrochemical events like cathodic activation and inflammatory species in pre-clinical testing.
Effect of Si addition on microstructure and performance of a biomedical Ti-Nb-Zr-Ta alloy prepared via powder hot extrusion
2024, Journal of Alloys and CompoundsIn this study, TNZT-xSi ((Ti53Nb35Zr7Ta5)100‐xSix, x = 0, 1.4, 2.3, wt.%) alloys are prepared by powder hot extrusion. The effect of Si addition on microstructure, mechanical properties, corrosion resistance and in vitro apatite formation ability of TNZT-xSi alloys is investigated. The as-extruded TNZT alloy mainly consists of elongated BCC grains. The addition of Si leads to the precipitation of fine (Ti, Zr)2Si (S2) particles from the BCC matrix. With the increase of Si content, the volume fraction of recrystallized grains rises significantly, and the microstructure of extruded alloys tends to transform from elongated to equiaxed grains. It’s indicated that the introduction of S2 particles activates the dynamic recrystallization process during hot extrusion and results in an obvious reduction in the overall grain size. Compared with the TNZT-0Si base alloy, the tensile strength of TNZT-2.3Si alloy is improved from 726 MPa to 983 MPa, with the elongation declining from 28.0% to 9.5%. The TNZT-xSi alloys exhibit higher corrosion potential (Ecorr) and lower corrosion current density (Icorr) than Ti-6Al-4V alloy in simulated body fluid, due to the formation of more stable oxides such as Nb2O5, ZrO2 and Ta2O5. Furthermore, TNZT-xSi alloys have apatite formation ability superior to Ti-6Al-4V. These results suggest that TNZT-xSi alloys may have the potential as a biomaterial for implant applications.