Obrabotka Metallov 2019 Vol. 21 No. 2

OBRABOTKAMETALLOV Vol. 21 No. 2 2019 133 MATERIAL SCIENCE Structure of Ti-40Nb Alloy Formed with High-Energy Methods Zhanna Kovalevskaya 1, 2, a , Yurii Sharkeev 1, 2, b , Margarita Khimich 1, 3, c, * , Anna Eroshenko 1, d , Pavel Uvarkin 1, e 1 Institute of Strength Physics ad Materials Sciences SB RAS, 2/4, pr. Akademicheskii, Tomsk, 634055, Russian Federation 2 National Research Tomsk Polytechnic University, 30 Lenin Avenue, Tomsk, 634050, Russian Federation 3 National Research Tomsk State University, 36 Lenin Avenue, Tomsk, 634050, Russian Federation a http://orcid.org/0000-0003-3040-8851, zhanna_kovalevskaya@mail.ru , b http://orcid.org/0000-0001-5037-245X , sharkeev@ispms.tsc.ru , c http://orcid.org/0000-0001-5859-7418, khimich@ispms.tsc.ru, d http://orcid.org/0000-0001-8812-9287, eroshenko@ispms.tsc.ru , e http://orcid.org/0000-0003-1169-3765 , uvarkin@ispms.tsc.ru Obrabotka metallov (tekhnologiya, oborudovanie, instrumenty) = Metal Working and Material Science. 2019 vol. 21 no. 2 pp. 124–135 ISSN: 1994-6309 (print) / 2541-819X (online) DOI: 10.17212/1994-6309-2019-21.2-124-135 Obrabotka metallov - Metal Working and Material Science Journal homepage: http://journals.nstu.ru/obrabotka_metallov ARTICLE INFO Article history : Received: 5 March 2019 Revised: 18 March 2019 Accepted: 11 April 2019 Available online: 15 June 2019 Keywords : Ti-40Nb alloy Arc melting Selective laser melting Severe plastic deformation Microstructure β-phase α’’-phase Segregation Implants Funding: This work was performed under the Fundamental Research Program of the State Academies of Sciences for 2013- 2020, line of research III.23.2.2. Acknowledgements: Authors are grateful to Q. Zhu, A.A. Saprykin, E.A. Ibragimov, E.V. Baba- kova, I.A. Glukhov, I.A. Shulepov for their participation and results discus- sion. ABSTRACT Introduction. Ti–40 wt. % Nb (Ti–40 Nb) is a non-conventional material for medical applications as it has low modulus of elasticity (50-60 GPa) which is of great importance for the mechanical compatibility of an implant with bone tissue. The progressive methods productions of finished items on Ti-40Nb alloy are severe plastic deformation (SPD) and selective laser melting (SLM). These methods have different nature and influence on phase composition, structure and properties of finished item. Due to this fact rigorous structural researches are required. Aim of present study is evaluation of structural characteristics of Ti–40 Nb alloy produced in conditions of high-energy influence via SPD and SLMmethods, taking into account heterogeneity of elemental composition, which is caused by the structure formation conditions. Object of research. Alloy ingots were produced via electro-arc melting. SPD of quenched ingots was carried out via combined method including subsequent operations of pressing to symmetric channel, multiaxial forging and rolling. SLM of mechanically alloyed powder was carried out with VARISKAF-100MVS installation. Research methods. Specimens’ structure was studied with the methods of optical and scanning electron microscopy, energy-dispersive microanalysis, X-ray diffraction analysis. Elastic modulus and nanohardness were estimated via unrestored print method. Results. It is shown that in the process of ingot’s crystallization dendritic structure, consisting of β-phase with intracrystalline segregation and Nb concentration’s difference up to 6 wt. %, is formed. After ingot’s quenching α’’-phase’s martensite structure is formed in Nb-depleted zones. Ingot’s SPD leads to the elimination of segregation, to the reverse α’’ → β + α transformation and to the formation of ultrafinegrained structure with the optimal complex of physical mechanical properties required for the implants production. SLM forms structure, consisting of β-phase grains of micron size with interlays of nonequilibrium α’’-phase throughout the grains’ boundaries. It is proposed to remove the formed in the alloy intracrytalline segregation with the difference of Nb concentrations up to 27 wt. % via subsequent thermal treatment. Conclusion. Two considered high-energy methods of medical implants production, which are SPD and SLM, have significant influence on the structure of Ti–40 Nb alloy. Character of the influence is defined with the method by itself and with the formed heterogeneity of elemental composition. For citation: Kovalevskaya Zh.G., Sharkeev Yu.P., Khimich M.A., Eroshenko A.Yu., Uvarkin P.V. Structure of Ti-40Nb alloy formed with high-energy methods. Obrabotka metallov (tekhnologiya, oborudovanie, instrumenty) = Metal Working and Material Science , 2019, vol. 21, no. 2, pp. 124–135. DOI: 10.17212/1994-6309-2019-21.2-124-135. (In Russian). ______ * Corresponding author Khimich Margarita A. , Junior Researcher, PhD Student Institute of Strength Physics and Materials Sciences SB RAS, National Research Tomsk State University, 2/4, pr. Akademicheskii, Tomsk, 634055, Russian Federation Tel.: +7-952-884-04-25, e-mail: khimich@ispms.tsc.ru