The department was founded in 1945. G.V. Kurdyumov, Member of the Ukrainian SSR A.S. headed the department. Since 1967, Dr. Sci. (Phys.-Math.), Prof. L.G. Khandros had headed the department. Since 1985 the Corresponding Member of the N.A.S. of Ukraine, Dr. Sci. (Tech.), Prof. Yu.M. Koval has been in charge of the department.
The unknown before phenomenon of a thermoelastic phase equilibrium during the phase transformations of the martensite type was predicted and experimentally determined (1948-1949). The phenomenon lies in formation of the elastic martensite crystals, boundaries of which within the transformation temperature interval at temperature alterations and (or) the stress field are shifting towards a martensitic or an initial phase with the simultaneous reversible change of the geometric shape of samples. The mentioned phenomenon was found by G.V. Kurdyumov and L.G. Khandros. It was registered in 1980 by State Inventions and Discoveries Committee of the USSR as a discovery ¹ 239 and was called the `Kurdyumov effect`.
Research of the crystals` formation of the martensite phases, as well as the found phenomenon changed cardinally the conception on a crystal lattice restructuring of the initial phases into martensite ones. It was determined that martensite transformations, as well as other phase transformations, occur by the way of formation and growth of the new phase crystals, and the velocity of their growth depends not only on cooling velocity but also on stress field in the sample. These studies became an experimental ground for the martensite transformation theory (G.V. Kurdyumov, L.G. Khandros).
The hyperelastic alloys` behavior caused by the formation of the martensite crystals under the action of stresses and their vanishing by unloading was found within the stability area of a high-temperature phase. Later, these effects were called as `shape memory` and `hyperelasticity` (L.G. Khandros, I.A. Arbuzova).
It was shown that a fine crystal structure (packing defects, fine twins) appears simultaneously with the formation of the martensite crystal (L.G. Khandros, V.A. Lobodiuk).
A nature of hyperelasticity and shape memory which appear in the alloys with thermoelastic martensite in the different temperature intervals was discovered during the cycle of the X-ray research, conducted on single crystal samples. During study a number of the new phases (6R, 12R, 17R, 7R), formed in the applied stress field, was found (V.V. Martynov, L.G. Khandros).
The effect of spontaneous deformation at the martensite transformation during cooling and further shape restitution at heating (bidirectional memory) was found and researched. It was determined that a partial relaxation of stresses increases, and the strengthening caused by the deformation, aging and alloying, reduces the hysteresis of martensite transformation (L.G. Khandros, P.V. Titov, I.A. Arbuzova, Yu.M. Koval, V.V. Martynov).
It was found that by alloying with gallium of the copper-tin alloys the alteration of the martensite transformation kinetics from explosive to isothermal one takes place (V.A. Lobodiuk, T.G. Sych).
The problem on thermoelastic phase equilibrium in the systems with random inner stresses was considered. It was shown that the problem on self-consistent equilibrium has been brought to solving the non-linear hysteresis equation for the effective field, defining both microstructural and macrostructural characteristics of a heterophase state. The method for solving of the mentioned equations was proposed (Yu.M. Koval, A.A.Likhachev).
A theoretical study of the dynamic aspects for the structural transformations of the martensite type within the mechanics and thermodynamics of the elastic continuous mediums was carried out. The equations were obtained for the laws of mobile equilibrium, appearing by martensite transformations of interphase boundaries (IPhB), which are considered as independent objects and which are the motive sources of the elastic and thermal fields in a crystal. At the same time they experience the action of braking forces from the side of these fields. It was shown that in the case of the martensite phase with twins the mobility of IPhB is higher than in martensite with dislocations (Yu.M. Koval, A.Yu. Pasko).
Nearby the equiatomic composition (TiNi) the change of structural and phase states was discovered and studied: appearing of the short-range order according to the structural vacancies and transition to the long-range order with the formation of a stable phase (X–phase, fcc, a=1,58 nm) (V.I.Kolomytsev, V.A. Lobodiuk).
On the research results of the alloying of the Ni-Ti alloys` influence on the martensite transformation parameters and shape memory effect there were developed the physical principals for alloying and thermomechanical treatment of these alloys to obtain the given characteristics (Yu.M. Koval, V.I. Kolomytsev, V.A. Lobodiuk, G.S. Firstov).
Using the examples of the Fe–Ni–Nb alloys it was shown that almost full shape memory effect could take place in the alloys at a relative high hysteresis and small tetragonality of the martensite lattice. Deformation of the particles separated during annealing is inelastic, includes in itself the shift and rotary components. It stipulates a high degree of the shape recovery (Yu.M. Koval, G.Ye. Monastyrskii).
The classification of the deformation mechanisms and shape recovery in the alloys with different character of the martensite transformations was proposed based on the conducted research activities. The criteria were defined which determine a full shape recovery during reverse martensite transformation (Yu.M. Koval).
On the foils of the functional alloys with complex alloying of the Ti–Ni–Hb system within the temperature interval (Tg–vitrification —Tx–crystallization) the superplasticity effect was found. The value of the effect reaches 60-70% of deformation and has temperature and speed (deformation speed) dependence (Yu.M. Koval, A.Yu. Sezonenko).
The experimental and theoretical justification for the effect with magnetic shape memory in the anisotropic ferromagnetic materials was given. The theoretical approach is based on the principles of conservation of energy, balance conception of the magnetic moving and pinning forces on twin-borders. The universal differential correlations for the pinning forces take into account appearing of the hysteresis. The materials were developed with the magnetic shape memory, demonstrating giant (6-10%) magneto-induced deformations (A.A. Likhachev).
The physical grounds for the development of composites with the magnetic shape memory were developed. The developed composites on NiMnGa base have rather high mechanical characteristics and demonstrate magneto-induced deformation up to 3,6 %. It is one order higher than in the usual striction materials (A.A. Likhachev).
The composite material on the base of functional alloys was developed. It has a low (close to invar) coefficient of thermal expansion in the temperature interval -50 -– +100 îÑ and high electrical conduction (Yu.M.Koval, Yu.V.Kudriavtsev, L.M. Neganov).
The basic principles of the nonequilibrium thermodynamics and kinetics of martensite transformations in homogeneous and gradient alloys with the shape memory effect were developed. The physical grounds were determined for obtaining of functional gradient materials. The laboratory specimens of gradient functional materials were obtained. The production methods of heat-sensitive gradient elements were developed (Yu.M. Koval, A.A. Likhachev, L.M. Neganov).
The thermo e.m.f. signal generation was found while occurring of MF. The reason for appearing of e.m.f. signals is connected with the formation of differential thermocouple austenite–martensite–austenite. For the first time it was experimentally shown that the reverse MF is realized due to the same kinetics as the direct one with the usage of the effect of e.m.f. signals appearing (Yu.M. Koval, V.P. Golovko).
Much success was achieved in creation of physical bases for development of new alloys with high temperature (higher than 300 °C) shape memory effect—quasi-binary intermetallic compounds of copper and nickel. The martensite transformation mechanism was determined in quasi-binary compounds Zr with high temperature shape memory effect: the growth of MF temperatures is provided with the prevalence of interaction Me–Me against the background of 3d-4d hybridization weakening of electron states of few electron and multiple electron atoms, and is supported with lower, comparing with austenite, density of martensite structures. The structure additionally stabilizes the martensite phases by heating due to the vibrating component of entropy (Yu.M. Koval, G.S. Firstov).
Non-thermoelastic MF in Zr compounds could be accompanied with full shape recovery at the shape memory effect. At that, such behavior is determined by the MF mechanism that includes an elastic interaction of austenite and two martensite phases which are appeared and disappeared by the specific non-thermoelastic way (Yu.M. Koval, G.S. Firstov).
It is managed to avoid the accumulation of plastic deformation at high temperature shape memory effect due to complication of MF crystallography as it was shown in intermetallic Ni3Ta compound, or by way of suppression of the diffusion processes, relaxation of the inner stresses at the increase of temperatures of alloys melting with the high temperature shape memory effect (as it was shown in HfIr compound) (Yu.M. Koval, G.S. Firstov).
Studying the influence of alloying with silver and tantalum, as well as technological factors on a structure and the properties of alloys with the shape memory effect on Ti–Ni base has given the opportunity to suggest an TiNiAgTa alloy for medical use (production of the bile duct dilator) (Yu.M. Koval, V.V. Odnosum, V.N.Slipchenko).
For the first time it was shown that highly-entropic materials are subjected to martensitic transformation, which is accompanied by the shape memory effect with 100 % of recovery. It was shown that for the highly-entropic intermetallic compounds of AB type (À-TiZrHf, Â-CoNiCu) the austenite structure could be put to the B2 type, and martensite one —to B19. Strengthening due to the formation of the solid solution of such highly-entropic material (two times higher in comparison to TiNi) causes the suppression of the plastic deformation processes which is appeared by way of a dislocation glide in a favour of the martensite mechanism (Yu.M.Koval, G.S.Firstiov).
It was found that the reason of structural instability of the martensitic character in the highly-entropic compounds of (TiZrHf)50(CoNiCu)50 system is presence of the interatomic interaction of two types A-A and B-B, where À-TiZrHf, Â-CoNiCu (Yu.M.Koval, G.S.Firstiov).
G.V. Kurdyumov, the head of the department, was awarded with U.S.S.R. State Prize for the achievements in metallurgy science in 1949.
The researchers of the department G.V. Kurdyumov, L.G.Khandros, I.A. Arbuzova, Yu.M.Koval, V.A. Lobodiuk, V.V.Martynov, P.V.Titov, V.I.Kolomytsev received an Ukr. S.S.R. State Prize for the cycle of research `Physical Nature of Thermoelastic Phases` Equilibrium, Hyperelasticity and Shape Memory by Martensite Transformations` in 1984.
The researchers of the Phase Transformations Department have been actively and successfully presenting their scientific results at the profile international conferences such as ICOMAT, ÅSOMAT and SMST for decades. Moreover, in 1977 the Phase Transformations Department took the lead in organization of the international conferences on martensite transformations `ICOMAT`, the first of which was held in Kyiv. Since that time the conferences `ICOMAT` have been held once in three years in different countries of the world and became the most authorized conference on martensite transformations. International acknowledgement of the scientific achievements of the department is shown in the fact that the Permanent Member of the International Organization Committee `ICOMAT` was Prof. L.G. Khandros since 1977 till 1986, since 1986 was the Corresponding member N.A.S. of Ukraine Yu.M. Koval (since 2004 he remains as an Honored Member of the Organization Committee), and in 2004 took this post. In 2015 Dr. Sci. (Phys.-Math.) G.S. Firstov was chosen as a member of the International Organization Committee of the European Symposium on martensite transformations `ESOMAT`.
The employees of the department published a reference book (O.M. Barabash, Yu.M. Koval `Crystal Structure of Metals and Alloys`, K., 1986, Naukova dumka, 598 p.) and four monographs (V.A. Lobodiuk, E.I.Estrin `Martensite Transformations`, 2009, M., Fizmatlit, p. 351 (in Russian); Yu.M. Koval, V.A. Lobodiuk `Deformation and Relaxation Phenomena by Martensite Type Transformations`, 2010, Kyiv, Naukova Dumka, p. 350 (in Russian); V.V.Kozyrskii, V.V. Kaplun, I.P. Radko, S.P. Kokhanivskii, O.A.Likhachev, G.S. Firstov `Methods, Technologies and Technical Devices to Increase the Reliability of Electrotechnical Equipment Based on Functional Materials`, Kyiv, KNUTD, 2012, 447 p.(in Ukrainian), V.A. Lobodyuk, E.I. Estrin «Martensitic transformations», England, Cambridge International Science Publishing, (CISP), 8.2014 (Ð.380) (in English). In 2013, Yu.M. Koval and V.A. Lobodyuk received the V.I. Trefilov Prize of the N.A.S. of Ukraine for the monograph `Deformation and Relaxation Phenomena by Martensite Type Transformations`.
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