Abstract
A comprehensive, bottoms-up characterization of two of the most widely used biomedical Ti-containing alloys, NiTi and β-Ti, was carried out applying a novel combination of neutron diffraction, neutron prompt-gamma activation, surface morphology, thermal analysis and mechanical tests, to relate composition, microstructure and physical-chemical-mechanical properties to unknown processing history. The commercial specimens studied are rectangular (0.43 × 0.64 mm~0.017 × 0.025 inch) wires, in both pre-formed U-shape and straight extended form. Practical performance was quantitatively linked to the influence of alloying elements, microstructure and thermo-mechanical processing. Results demonstrated that the microstructure and phase composition of β-Ti strongly depended on the composition, phase-stabilizing elements in particular, in that the 10.2 wt.% Mo content in Azdent resulted in 41.2% α phase, while Ormco with 11.6 wt.% Mo contained only β phase. Although the existence of α phase is probable in the meta-stable alloy, the α phase has never been quantified before. Further, the phase transformation behavior of NiTi directly arose from the microstructure, whilst being highly influenced by thermo-mechanical history. A strong correlation (r = 0.878) was established between phase transformation temperature and the force levels observed in bending test at body temperature, reconfirming that structure determines performance, while also being highly influenced by thermo-mechanical history. The novel methodology described is evidenced as generating a predictive profile of the eventual biomechanical properties and practical performance of the commercial materials. Overall, the work encompasses a reproducible and comprehensive approach expected to aid in future optimization and rational design of devices of metallic origin.
Highlights
Ti and Ti-containing alloys have an extreme strength-to-weight ratio, high corrosion resistance, biocompatibility and inherent ability to osseointegrate, making them ideal for biomedical applications
The majority of the wires have on average larger dimensions in height and smaller dimensions in width with respect to standard sizes (Table 1), with NiTi wires showing an average deviation of 1.95% in height (~8.4 μm)
0.64, the value spread is high as evidenced by the higher standard deviation (SD). β-Ti wires showed the least accuracy in both height (2.1% Dev~9.0 μm) and width (2.9% Dev~18.6 μm)
Summary
Ti and Ti-containing alloys have an extreme strength-to-weight ratio, high corrosion resistance, biocompatibility and inherent ability to osseointegrate, making them ideal for biomedical applications It was not until the discovery of NiTi shape-memory alloy (trade name Nitinol) in 1961 and subsequent establishment of practical efforts to Metals 2022, 12, 406. Ti and Ti-containing alloys have an extreme strength-to-weight ratio, high corrosion resistance, biocompatibility and inherent ability to osseointegrate, making them ideal for 2 of biomedical applications It was not until the discovery of NiTi shape-memory alloy (trade name Nitinol) in 1961 and subsequent establishment of practical efforts to commercialize the alloy, did Ti alloys become widely used in industrial, commercial and commercialize the alloy, did Ti alloys become widely used in industrial, commercial and medical products. NiTi is composed of near equiatomic ratios of Ni and Ti, where the high temperature stable parent phase B2-Austenite may transform to the low temperature high temperature stable parent phase B2-Austenite may transform to the low temperature stable stable phase phase B19-Martensite
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
