Microstructure and mechanical behavior of metal injection molded Ti–Nb binary alloys as biomedical material

Abstract

The application of titanium (Ti) based biomedical materials which are widely used at present, such as commercially pure titanium (CP-Ti) and Ti-6Al-4V, are limited by the mismatch of Young's modulus between the implant and the bones, the high costs of products, and the difficulty of producing complex shapes of materials by conventional methods. Niobium (Nb) is a non-toxic element with strong β stabilizing effect in Ti alloys, which makes Ti-Nb based alloys attractive for implant application. Metal injection molding (MIM) is a cost-efficient near-net shape process. Thus, it attracts growing interest for the processing of Ti and Ti alloys as biomaterial. In this investigation, metal injection molding was applied to the fabrication of a series of Ti-Nb binary alloys with niobium content ranging from 10wt% to 22wt%, and CP-Ti for comparison. Specimens were characterized by melt extraction, optical microscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). Titanium carbide formation was observed in all the as-sintered Ti-Nb binary alloys but not in the as-sintered CP-Ti. Selected area electron diffraction (SAED) patterns revealed that the carbides are Ti2C. It was found that with increasing niobium content from 0% to 22%, the porosity increased from about 1.6% to 5.8%, and the carbide area fraction increased from 0% to about 1.8% in the as-sintered samples. The effects of niobium content, porosity and titanium carbides on mechanical properties have been discussed. The as-sintered Ti-Nb specimens exhibited an excellent combination of high tensile strength and low Young's modulus, but relatively low ductility.

Effects of Mo Addition on the Mechanical Properties and Microstructures of Ti-Mn Alloys Fabricated by Metal Injection Molding for Biomedical Applications

“…Because both TMM-64 and Ti-9Mn have a higher Mo eq and more stable β phase than TMM-53 and Ti-6Mn, respectively, it is apparent that the solubility of C is more dependent on the stability of the β phase than on which stabilizer element is included. Similar observations were reported for Ti-Nb alloys 41) . The OM and XRD analyses only show the presence of β-phase, whereas the presence of an athermal ω phase is conrmed by TEM observations.…”

“…Further, compared to the TMM alloys fabricated by CCLM 23) , the amount of athermal ω phase is lower for all alloys fabricated by MIM, leading to lower Young s moduli. The presence of pores causes E to decrease 41) . On the other hand, the presence of carbides, which have a higher Young s modulus, causes E to increase.…”

“…Further, similar to the TiMn alloys fabricated by MIM, high O content and the presence of carbides can increase the UTS, while the presence of pores can decrease it. Overall, the low elongation of the TMM alloys is attributed to the high O content, and the presence of pores and carbides, which tend to decrease the ductility of the alloys 31,40,41) . The increase in elongation from 2.0% in TMM-53 to 5.0% in TMM-64 is attributed to the decrease in the amount of pores in the alloys, from 6.4% in TMM-53 to 4.8% in TMM-64.…”

Metal injection moulding of titanium and titanium alloys: Challenges and recent development

“…The alloys include but are not limited to: Ti-15V-3Cr-3Sn-3Al [114], Ti24Nb-4Sn-8Zr, TiNi [115], Ti-Nb-Zr [69], Ti-Mo [67], Ti-Mn [68] and Ti-Nb [60,[116][117][118].…”

Evolution of strength and structure during SPD processing of Ti–45Nb alloys: experiments and simulations

“…In recent years, TiNb based alloys are getting more attention in biomedical research areas because of the unique combination of their properties such as high specific strength, good corrosion resistance and excellent biocompatibility compared to other traditional alloys [1][2][3]. The alloys used for implants should have Young's moduli close to those of human bones (around 30 GPa) as this condition minimizes the stress shielding effect [4].…”