Conventional XRD and Micro-XRD Study of New Ternary Titanium Alloys

New titanium alloys with improved biocompatibility and wide range for elastic modulus have been developed for dental and biomedical applications. Properties of these alloys depend on their microstructural phases. Objective: Use conventional x-ray diffraction and Micro-XRD to determine the phases in Ti-30Ta-XNb, Ti-30Ta-XZr, Ti-30Nb-XTa and Ti-30Nb-XZr alloys, where X = 3, 7, 10 and 15 (wt %). Methods: Alloys were prepared by arc melting and homogenized 24 hr at 1000°C in an argon atmosphere. Conventional XRD was performed on 16 specimens (one for each alloy), and Micro-XRD was performed at 2-3 sites on each specimen and more sites for specimens with substantial compositional variation. For conventional XRD (Rint-2000, Rigaku), CuKa radiation was employed at 40kV and tube current of 100 mA. For Micro-XRD (Rint-2000), the tube current was 300 mA. The diameter of each Micro-XRD analysis site was approximately 100 µm. Results: Conventional XRD showed that all peaks for Ti-30Ta-3Nb and Ti-30Ta-7Nb were for alpha-titanium, but Ti-30Ta-10Nb had the 211 peak for beta-titanium and Ti-30Ta-15Nb had four major peaks (110, 200, 211 and 310) for beta-titanium. For Ti-30Ta-XZr, all spectra had major peaks for alpha-titanium with some peaks for beta-titanium. For Ti-30Nb-XZr, all spectra had major peaks for beta-titanium, and only Ti-30Nb-7Zr showed 101 and 102 peaks for alpha-titanium. For Ti-30Nb-XTa, most peaks were assigned to beta-titanium, but Ti-30Nb-3Ta and Ti-30Nb-7Ta also had peaks for alpha-titanium. Some ω-phase peaks may also occur for Ti-30Nb-7Ta. Micro-XRD analyses were generally consistent with conventional XRD from larger regions of approximately 1 cm diameter, but variations in proportions of phases were often observed at different sites. Conclusions: Depending upon composition, at room temperature these alloys are entirely alpha-titanium, largely beta-titanium, or mixture of alpha-titanium and beta-titanium. Micro-XRD showed that substantial variation in phases could occur at different sites on the same specimen.