In this study, the effect of molybdenum content in Ti-15Zr-based alloys (wt%) was analyzed in terms of crystalline structure, microstructure, selected mechanical properties, and cytotoxicity. The samples were produced by argon arc-melting followed by hot rolling and heat treatment processes. The crystalline structure and microstructure were dependent of both alloying elements (zirconium and molybdenum). Ti-15Zr alloy displayed only laths of a 0 phase, while the alloys up to Ti-15Zr-10Mo exhibited different proportions of a 0 , a", and b phases. Molybdenum content higher than 12.5 wt% fully stabilized the b phase. Vickers microhardness values of Ti-15Zr-Mo alloys were higher than those of CP-Ti due to solid solution and phase precipitation strengthening. Young's modulus values of Ti-15Zr-Mo alloys were lower than those of CP-Ti due to b phase stabilization. Cytotoxicity levels of Ti-15Zr-Mo alloys were within a tolerable range for biomedical purposes. In addition, we observed molybdenum content in Ti-15Zr-based alloys promoted an increase on pre-osteoblast adhesion up to 3 h of adhesion's time. Thus, Ti-15Zr-15Mo alloy presented better combination of properties than some traditional metallic biomaterials.

j m a t e r r e s t e c h n o l . 2 0 1 5;4(2):180-185 w w w . j m r t . c o m . b r Biomaterials Microstructure a b s t r a c t Titanium alloys have excellent biocompatibility, and combined with their low elastic modulus, become more efficient when applied in orthopedic prostheses. Samples of Ti-15Mo-Zr and Ti-15Zr-Mo system alloys were prepared using an arc-melting furnace with argon atmosphere. The chemical quantitative analysis was performed using an optical emission spectrometer with inductively coupled plasma and thermal conductivity difference. The X-ray diffractograms, allied with optical microscopy, revealed the structure and microstructure of the samples. The mechanical analysis was evaluated by Vickers microhardness measurements. The structure and microstructure of alloys were sensitive to molybdenum and zirconium concentration, presenting ␣ , ␣ and ␤ phases. Molybdenum proved to have greater ␤-stabilizer action than zirconium. Microhardness was changed with addition of molybdenum and zirconium, having Ti-15Zr-10Mo (436 ± 2 HV) and Ti-15Mo-10Zr (378 ± 4 HV) the highest values in each system.

Due to excellent biocompatibility and corrosion resistance, the application of titanium alloys in orthopedic and dental implants has been increasing since the 1970s. However, the elasticity of these alloys as measured by their Young’s modulus is still about two to four times higher than that of human cortical bone. The most widely used titanium alloy for biomedical applications is Ti-6Al-4V, however, previous studies have shown that the vanadium used in this alloy causes allergic reactions in human tissue and aluminum, also used in the alloy, has been associated with neurological disorders. To solve this problem, new titanium alloys without the presence of these elements and with the addition of different elements, usually beta-stabilizers, are being developed. Manganese is a strong candidate as an alloying element for the development of new beta-type titanium alloys, due to its abundance and low cytotoxicity. In this study, Ti-10Mo-5Mn, Ti-15Mo-2.5Mn and Ti-15Mo-5Mn alloys were prepared in an arc furnace, which resulted in an alloy structure clearly showing the predominance of the beta phase with a body-centered cubic crystalline structure. The observed microstructure confirmed the results on the structural characterization of alloys. Measurement of the indirect cytotoxicity of the alloys showed that the extracts of the studied alloys are not cytotoxic for fibroblastic cells.