Structural, physical, chemical, and biological surface characterization of thermomechanically treated Ti‐Nb‐based alloys for bone implants

Abstract

Metastable near‐beta Ti‐21.8Nb‐6Zr and Ti‐19.7Nb‐5.8Ta (at%) alloys were subjected to a thermomechanical treatment comprising cold rolling (CR) with a true strain of e = 0.3 and post‐deformation annealing (PDA) in the 500–900°C temperature range to ensure the superelastic behavior which is important for bone implants. It was found that PDA resulted in formation of about 1–2 μm‐thick oxide layer on the Ti‐Nb‐Zr and Ti‐Nb‐Ta alloy samples; the layer was mainly composed of TiO2, in rutile and anatase modifications. The structure, the phase and chemical compositions, and some surface‐sensitive properties of the alloys were compared to those of Ti‐50.7Ni and Ti‐Grade2 reference materials. These surface layers (especially that of the Ti‐Nb‐Zr alloy) demonstrated a promising combination of high cohesion strength (load causing surface layer fracture is over 25 N), hardness (∼12 GPa), and hydrophilicity (contact angle ∼40°). Surface modification by controlled oxidation during air annealing increases corrosion resistance and enhances in vivo osteoinductive properties of Ti‐Nb‐Zr alloys by changing the surface microrelief, increasing the surface wettability, and improving the mechanical characteristics, thus laying the foundation for the development of medical implants with prolonged service life. So, it was confirmed that the same thermomechanical treatment, which creates conditions for the superelastic behavior of the bulk metal (CR: e = 0.3 + PDA = 500–700°C for 1 hr), would also create a strong, protective and biocompatible layer on the implant surface.

Surface Modification of Biomedical Ti-18Zr-15Nb Alloy by Atomic Layer Deposition and Ag Nanoparticles Decoration

“…The development of new approaches to surface modification of such alloys is a relevant issue. So far, many contemporary surface modification methods have been applied to enhance the biological activity of T-Zr-Nb-based SMAs [19][20][21][22][23][24][25][26][27][28]. Most of them, such as anodization [19,21], plasma electrolytic oxidation [24] and thermal oxidation [25,26], are related to the formation of a surface layer based on the oxides of the main components of the alloy: TiO 2 , NbO 2 , Nb 2 O 5 and ZrO 2 .…”

“…So far, many contemporary surface modification methods have been applied to enhance the biological activity of T-Zr-Nb-based SMAs [19][20][21][22][23][24][25][26][27][28]. Most of them, such as anodization [19,21], plasma electrolytic oxidation [24] and thermal oxidation [25,26], are related to the formation of a surface layer based on the oxides of the main components of the alloy: TiO 2 , NbO 2 , Nb 2 O 5 and ZrO 2 . In some cases, it is also possible to form more complex oxides containing two main alloy components such as TiNbO 4 and TiNb 2 O 7 [25,26].…”

Effect of High-Pressure Torsion and Annealing on the Structure, Phase Composition, and Microhardness of the Ti-18Zr-15Nb (at. %) Alloy

“…This dissimilarity leads to development of “stress-shielding effect”, and the bone undergoes resorption of the tissue around the implant [ 2 ]. The solution to this problem is the use of alloys with a lower elastic modulus (30–50 GPa), such as metastable “beta” titanium alloys of the Ti-Nb-Zr system [ 3 , 4 , 5 , 6 , 7 ].…”

Structural analysis of a Nb-based alloy for biomedical application

“…Much research is being developed to characterize the mechanical and biochemical behavior of beta (b) titanium alloys, depending on the processes of obtaining and thermomechanical treatments of these alloys, which greatly influence their properties [1,2] . Among several Ti-based alloys, a binary composition like Ti-Nb is studied for application in biomaterials [3][4][5][6] .…”