Biocompatibility of new low-cost (α + ß)-type Ti-Mo-Fe alloys for long-term implantation.

In this work, two new α +â€¯ß titanium alloys with low contents of ubiquitous and low-cost alloying elements (i.e., Mo and Fe) were designed on the basis of the electronic parameters and molybdenum equivalent approaches. The designed Ti - 2Mo - 0.5Fe at. % (TMF6) and Ti - 3Mo - 0.5Fe at. % (TMF8) alloys were produced using arc melting process for studying their mechanical, electrochemical and cytotoxicity compatibilities and comparing these compatibilities to those of Ti-6Al-4V ELI alloy. The cost of the used raw materials for producing the TMF6 and TMF8 alloys are almost 1/6 of those for producing the Ti-6Al-4V ELI alloy. The hardness of the two alloys are higher than that of the Ti-6Al-4V ELI alloy, while their Young's moduli (in the range of 85-82 GPa) are lower than that of the Ti-6Al-4V ELI alloy (110 GPa). Increasing the Mo equivalent from 6 (in TMF6 alloy) to 8 (in TMF8 alloy) led to an increase in the plastic strain percent from 4% to 17%, respectively, and a decrease in the ultimate tensile strength from 949 MPa to 800 MPa, respectively. The microstructure of TMF6 alloy consists of α'/α″ phases, while TMF8 alloy substantially consists of α″ phase. The corrosion current densities and the film resistances of the new alloys are in the range of 0.70-1.07 nA/cm2 and on the order of 105â€¯Ω·cm2, respectively. These values are more compatible with biomedical applications than those measured for the Ti-6Al-4V ELI alloy. Furthermore, the cell viabilities of the TMF6 and TMF8 alloys indicate their improved compatibility compared to that of the Ti-6Al-4V ELI alloy. The CCK-8 (Cell Counting Kit-8) assay was conducted to investigate the cytotoxicity, proliferation, and shape index of the cells of the candidate alloys. Overall, the measured compatibility of the new V-free low-cost alloys, particularly TMF8, makes them promising candidates for replacing the Ti-6Al-4V ELI alloy in biomedical applications.

Superelasticity Evaluation of the Biocompatible Ti-17Nb-6Ta Alloy.

Recently, studying the shape memory effect of the biocompatible Ti alloys takes much attention in the biomedical and healthcare applications. This study concerns about characterizing the superelasticity of the new biocompatible Ti-17Nb-6Ta (TNT) alloy. Microstructure of TNT was observed using optical and confocal microscopes. The alloy consists of two phases: ß (predominant phase) and α″ martensite phase. The influence of cold rolling deformation on the microstructure was illustrated in which the martensitic-induced transformation appeared by cold rolling. The alloy is ductile as only the fracture dimples appeared in its fracture surface. Multicyclic loading and deloading tensile testing was applied to TNT specimens (flat and wire shapes) in order to evaluate the superelasticity. A superelastic strain as high as 3.5% was recorded for this TNT alloy. Therefore, TNT alloy has high potential for many biomedical and healthcare applications.

Probing Nanoscale Phase Separation at Atomic Resolution within ß-Type Ti-Mn Alloy: A Potential Candidate for Biomedical Implants.

Biocompatible ß-type Ti alloys with high ultimate tensile strength (UTS) and yield strength are potential candidates for certain orthopedic and cardiovascular implants. Aiming for these applications, Ti alloy with 14 wt % Mn (Ti-14 Mn) as ß-stabilizer was processed through thermomechanical treatment along with solutionizing and quenching, followed by 95% cold rolling, which resulted in ultrahigh UTS and yield strength. 3-[4,5-Dimethylthiazol-2-yl]-2,5-diphenyltetrazolimbromide assay with different cell lines suggests efficient cell growth on alloy surface without compromising biocompatibility. Cell adhesion and spreading assay show that cells are not only able to attach to the alloy surface but also able to spread and grow with normal morphology, which projects this material as a potential candidate for biomedical application. Previous studies on binary ß-type Ti alloy systems treated with the above-mentioned processing route confirm the presence of nanoscale phase separation, which enhances its mechanical properties. To discover the same phenomena in the alloy of the present study, bright-field and high-resolution transmission electron microscopy (HRTEM) imaging experiments were performed and nanoscale contrast-modulated lamella regions were observed. Geometrical phase analysis on complex-valued exit wave, reconstructed using focal series HRTEM images, demonstrates that the lamella is a result of d-spacing modulation. Ab initio calculation indicates that d-spacing modulation with the same crystal structure occurs due to composition modulation and was proved by scanning transmission electron microscopy imaging coupled with quantitative energy-dispersive X-ray spectroscopy. Correlating contrast, strain, and composition modulation confirms nanoscale phase separation, which is the first report of this phenomenon in Ti-Mn alloy system.

Biocompatibility of new Ti-Nb-Ta base alloys.

ß-type titanium alloys are promising materials in the field of medical implants. The effect of ß-phase stability on the mechanical properties, corrosion resistance and cytotoxicity of a newly designed ß-type (Ti77Nb17Ta6) biocompatible alloys are studied. The ß-phase stability was controlled by the addition of small quantities of Fe and O. X-ray diffraction and microstructural analysis showed that the addition of O and Fe stabilized the ß-phase in the treated solution condition. The strength and hardness have increased with the increase in ß-phase stability while ductility and Young's modulus have decreased. The potentio-dynamic polarization tests showed that the corrosion resistance of the new alloys is better than Ti-6Al-4V alloy by at least ten times. Neutral red uptake assay cytotoxicity test showed cell viability of at least 95%. The new alloys are promising candidates for biomedical applications due to their high mechanical properties, corrosion resistance, and reduced cytotoxicity.