ISSN 1063-7842, Technical Physics, 2013, Vol. 58, No. 10, pp. 1432–1436. © Pleiades Publishing, Ltd., 2013. Original Russian Text © V.I. Betekhtin, Yu.R. Kolobov, O.A. Golosova, B.K. Kardashev, A.G. Kadomtsev, M.V. Narykova, M.B. Ivanov, T.N. Vershinina, 2013, published in Zhurnal Tekhnicheskoi Fiziki, 2013, Vol. 83, No. 10, pp. 38–43. 1432 INTRODUCTION Interest in titanium and titanium-based alloys is caused by a unique combination of its properties, namely, a high strength, a low density, and a low elastic modulus. The last feature is important for developing biomedical alloys, since such materials must have both biochemical compatibility with human being tissues, which consists in the absence of immune reactions and inflammatory processes, and biomechanical compati- bility, which determines the functional reliability of implants [1–4]. The main characteristic of the biome- chanical compatibility of an implanted material is the elastic modulus, which should be as close as possible to the elastic modulus of the bone (30 GPa). This close- ness makes it possible to avoid the so-called stress- shielding effect, which manifests itself in inevitable bone resorption (bone dissolution because of osteo- clast activity) in the region without mechanical loads and, in contrast, at the sites of excess stress and strain concentrations (which are higher than those typical of normal functioning of bone structures) [5]. From this standpoint, titanium β alloys with a low elastic modulus, which is close to that of the bone tis- sue, are of particular interest for application as a mate- rial for implantology [3, 6]. A decrease in the elastic modulus of titanium alloys is achieved by introducing a set of certain β-stabilizing alloying elements except for V, Al, Ni, and Co, which exert an allergic action on living tissues or a general toxic action on a human being [1, 7, 8]. At present, alloying with niobium, molybdenum, and zirconium is most promising. Tita- nium-based alloys with these elements have a low elas- tic modulus, a high corrosion resistance, and a mechanical strength sufficient for most applications; in addition, they are ductile and manufacturable [9]. The purpose of this work is to study the effect of thermomechanical treatment (rolling followed by annealing) on the elastic modulus, the amplitude- independent damping ratio, the microplastic flow stress, and the density of a Ti–26Nb–7Mo–12Zr tita- nium β alloy using an acoustic resonance method and densimetry. EXPERIMENTAL As a starting material, we chose a titanium β alloy containing 55% Ti, 26% Nb, 7% Mo, and 12% Zr (Ti– 26Nb–7Mo–12Zr) with an average grain size of 280 ± 9 μm; it was fabricated by vacuum arc remelting at OAO VSMPO-AVISMA (Verkhnyaya Salda, Russia) followed by forging at temperatures above the recrys- tallization temperature. The thermomechanical treatment (TMT) of the alloy consisted in sheet rolling followed by recrystalli- zation annealing. Rolling was performed without heating (at room temperature) at a reduction of 100– 200 μm per pass to a total reduction of 30, 60, and 90%. The prepared samples were subjected to anneal- ing at 850°C followed by water quenching. To study the elastoplastic properties, we used an acoustic resonance method performed with a com- pound piezoelectric vibrator at a longitudinal vibra- tion frequency of about 100 kHz. The elastic modulus and the amplitude-independent damping ratio were measured over a wide vibrational strain amplitude range. We used moderate amplitudes to retain the dis- location structure of the samples: after acoustic Elastoplastic Properties of a Low-Modulus Titanium-Based β Alloy V. I. Betekhtin a *, Yu. R. Kolobov b, c , O. A. Golosova b , B. K. Kardashev a , A. G. Kadomtsev a , M. V. Narykova a , M. B. Ivanov b , and T. N. Vershinina b a Ioffe Physical Technical Institute, Russian Academy of Sciences, Politekhnicheskaya ul. 26, St. Petersburg, 194021 Russia *e-mail: Vladimir.Betekhtin@mail.ioffe.ru b Research–Educational Center Nanostructured Materials and Nanotechnologies, Belgorod State University, ul. Pobedy 85, Belgorod, 308015 Russia c Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, Moscow oblast, 142432 Russia Received September 10, 2012; in final form, December 19, 2012 Abstract—The elastoplastic properties (elastic modulus, amplitude-independent damping ratio, microplas- tic flow stress) of a Ti–26Nb–7Mo–12Zr titanium β alloy are determined using an acoustic resonance method. The effect of the strain during thermomechanical treatment on the structural features of the micro- crystalline alloy and, hence, its elastoplastic properties is analyzed. DOI: 10.1134/S1063784213100046 SOLID STATE