Mechanical and Microstructural Characterization of AS-CAST Ti-12Mo-xNb Alloys for Orthopedic Application

Abstract

The development of β-metastable titanium alloys that combine low Young's modulus, good mechanical properties, corrosion resistance and biocompatibility has attracted industry interest. This type of alloy is an alternative to commercial alloys such as Ti-6Al-4V, avoiding the cytotoxic effect that occurs with Al and V in the human body in the manufactured orthopedic prostheses. In this scenario, the present work aims to characterize the effect of Nb concentration in the properties of Ti alloys based on the Ti-12Mo-xNb stoichiometry (x = 0, 3, 8, 13, 17 and 20). All alloys were produced by arc melting with non-consumable tungsten electrode in an argon atmosphere and the ingots were characterized by x-ray diffraction (XRD), optical microscopy (OM), Vickers microhardness and Young's modulus was measured by impulse excitation and density was measured using the Archimedes' principle. The Ti-12Mo alloy and the Ti-12Mo-20Nb alloy showed the lowest Young's modulus. The best hardness/ modulus was found for the Ti-12Mo-3Nb alloy. All the alloys studied in this work showed hardness/ modulus ratio above the traditional Ti-6Al-4V alloy (2.85), presented great potential for the biomedical application.

Characterization and Comparison of Mechanical Properties and Corrosion Resistance of Ti-10mo-20nb, Ti-6al-4v and Ti-Cp Alloys for Biomedical Applications

“…The hardness average value of the Ti-10Mo-20Nb alloy was approximately 238 ± 11.4 HV, the same procedure was adopted for the Ti-cp and Ti-6Al-4V samples and displayed the values of 170 ± 19 HV and 340 ± 24 HV, respectively. This occurs since, the addition of the element Mo, the alloy has a tendency to increase the value of mechanical strength (LI et al, 2020), moreover, a higher Nb content acts by decreasing the hardness value, due to Nb be a stabilizer of the β phase preventing the formation of other phases that increase hardness, such as α' (hexagonal martensite), α' (orthorhombic martensite) and ω (omega phase) (BAHL et al, 2020;COSSÚ et al, 2019). This explains the hardness reduction behavior when compared to Ti-6Al-4V alloy.…”

“…The Ti-cp and Ti-6Al-4V alloys have the highest elastic modulus, 112.5 ± 7.5 GPa and 113.5 ± 10.5 GPa respectively, Ti-10Mo-20Nb, on the other hand, has an elastic modulus of 74 ± 4 GPa, which is closer to the value of 15.68 ± 4.4 GPa for the bones. The decay in the average value of the Ti-10Mo-20Nb alloy is justified by the alloy elements Nb and Mo which tend to decrease the elastic modulus as the percentage content of the two elements tend to increase (COSSÚ et al, 2019;LI et al, 2020). It is more interesting that the required value of the E is as close as possible to the bones as well as to the hardness, in order to mitigate the effects of stress shielding (JOSHI et al, 2000;SUL, 2003).…”