Actual Problems in Machine Building 2018 Vol. 5 No. 3-4

Actual Problems in Machine Building. Vol. 5. N 3-4. 2018 Materials Science in Machine Building ____________________________________________________________________ 100 УДК 620.18 MICROSTRUCTURE AND MECHANICAL PROPERTIES OF AS-CAST Ti-Nb ALLOYS * Thoemmes A., Ph.D. student (NSTU, Novosibirsk) Thoemmes A . – 630073, Novosibirsk, 20 Prospekt K. Marksa Novosibirsk State Technical University, Russian Federation e-mail: thoemmes.alexander@gmail.com The effect of Nb content on microstructure, mechanical properties and phase formation in suction cast binary Ti-Nb alloys was investigated using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and Synchrotron X-ray diffraction (SXRD) analysis. The content of Nb varied in the range 30-35 mass % leading to significant changes in the microstructure. The as-cast binary Ti-Nb samples exhibit β + α``+ ω phases at a composition of 30 mass % Nb and β + ω at 35 mass % Nb. The fraction of metastable ω decreases with increasing the Nb content. As a result, the microhardness decreases from 301 ± 7 HV 0.05 to 222 ± 5 HV 0.05 . Keywords: Titanium alloys, Biomaterials, Metastable phases Introduction The growing progress in the medical field led to an increasing demand of a new generation of metallic biomaterials [1]. Currently in use are stainless steels, Cr-Co alloys and Ti alloys. These materials are in service since decades. Their release of toxic metal ions can cause health problems like allergies, Alzheimer`s or Parkinson`s diseases [2–5]. The big difference in Young`s modulus between a metallic implant and a human bone causes an effect called stress shielding, which leads to subsequent loosening of the implants [6]. The ideal metallic biomaterial for implant applications should exhibit excellent biocompatibility, superior corrosion resistance, high strength and a low Young`s modulus [7; 8]. A large number of studies have been carried out to develop such a material [9–16]. Previous studies reported that Ti-Nb alloys show considerably better mechanical properties and a lower Young`s modulus than the nowadays mostly used Ti-alloy for biomedical application. Previous study [17] has showed that the microstructure and mechanical properties of Ti-Nb alloys are very sensitive to the Nb content. In annealed alloys with less than 24 mass % Nb an acicular martensitic structure was visible, whereas if the Nb content increases equiaxed β grains are visible. Depending on the Nb content and cooling rate after heat treatment a formation of metastable ω phase is possible. The aim of this work is to investigate the influence of Nb content on microstructure, phase formation and mechanical properties of cold crucible cast alloys. * Acknowledgements The work was financially supported by the Russian Federation via the Ministry of Education and Science of the Russian Federation (Agreement No. 14.610.21.0013, project identifier RFMEFI61017X0013). Materials characterization was carried out at NSTU Materials Research Center.