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The results of a study of structure, phase, and chemical compositions of nanostructured (Ti,Zr)N coatings formed by vacuum arc deposition on Ti0.16Pd (wt.%) alloy substrates are reported. The coating composition was varied depending on the quasi-binary system δ—TiN—δ—ZrN. The coatings were formed in two modes: without (mode 1) and with (mode 2) rotation of the substrates in a plasma flow. It was shown that irrespective of the deposition regime, the coatings have a single-phase nanograined (grain size ≤ 20 nm) structure of δ-nitrides TiN, (Ti,Zr)N, and ZrN. It is found out that the coatings deposited in accordance with modes 1 and 2 significantly differ in their microstructure. It is demonstrated that in the case of electrolytic hydrogenation in a physiological saline solution (0.9% NaCl), the barrier properties of the coatings deposited via mode 2 are substantially better than those deposited via mode 1 (irrespective of the chemical coating compositions). In the coatings with a regular columnar structure (mode 1), there is a high concentration of hydrogen homogeneously distributed over the coating thickness. In the coatings formed via mode 2 (without columnar microstructure), a high concentration of hydrogen was observed in the subsurface area only. It is found out that there is no hydrogen diffusion into the substrate of these coating both immediately after hydrogenation and after storing for 430 h at room temperature. It was shown that the highest barrier properties were exhibited by the (Ti,Zr)N coatings with the least correlation of spatial distribution of nanograins and Zr/Ti ≤ 1. The hydrogen absorption in the coating based on zirconium nitride increases by a factor of 2.

Here we analyze the microstructure and phase composition of a Ti alloy with 0.16Pd and 0.14Fe (wt%) alloy exposed to warm equal channel angular pressing (ECAP) at 648 K. The analysis shows that after four ECAP passes, the material assumes a submicrocrystalline structure with an average grain size of 0.28 μm, as against its initial value 10 μm, and that the α phase dominates in the alloy both before and after ECAP. The initial alloy reveals a high content of Fe and Pd atoms near grain boundaries compared to central grain regions. Such near-boundary zones contain orthorhombic α′′ martensite in addition to the α phase, and β or α + β particles are found directly at the grain boundaries. These features of the phase composition are inherited after ECAP. The yield strength of the ECAP treated alloy is 500 MPa, being greater than the initial strength 350 MPa, and its margin of plasticity is rather high. The torsional strain up to fracture in the initial and in the ECAP treated alloy is 70% and 50%, respectively.

It is shown that in alloys with thermoelastic martensitic transformations, shape memory and superelasticity effects, the real yield stress (τ0.3) can be determined only by a joint analysis of “stress-total strain” and “plastic deformation-total strain” dependences. We suggest to determine of the dependence of the “plastic deformation – total deformation” from isothermal cycles of “loading at successively increasing values of the applied external stress – unloading” and the subsequent heating of unloaded specimens up to finish of the return of inelastic martensitic deformation. The residual deformation equals to the plastic deformation in this case. Using Ti49.2Ni50.8 (at%) binary alloy specimens whose structure was changed from coarse-grained to micro- and submicrocrystalline by means of warm rolling, the yield point τ0.3 in torsion of specimens was demonstrated to be localized on “τ-γ” dependence at the end of pseudo- yield plateau or at the beginning of the subsequent linear section of deformation development under loading. The development of plastic deformation at τ > τ0.3 was also studied.

The paper presents the results of a study the hydrogen effect on the structural-phase transformations and the superelasticity in binary ultrafine-grained (UFG) TiNi based alloy after diffusion redistribution hydrogen as a result of aging at room temperature. The redistribution of hydrogen in the process of long-term aging after electrolytic hydrogenation of UFG wire specimens the Ti49,1Ni50,9(at.%) stabilizes the B2 structure. Superelasticity in samples aged at room temperature after hydrogenation is significantly deteriorated.

This paper presents experimental data on the microstructure and martensite transformation temperatures of Ti49.8Ni50.2 (at%) after abc pressing (multi-axial forging) to different true strains e from 1.84 to 9.55 at 573 K. The data show that increasing the true strain results in grain–subgrain refinement on different scales at a time. With e = 9.55 at 573 K, the average grain–subgrain size measured approximately 130 nm. Decreasing the abc pressing temperature from 723 to 573 K caused a decrease in all martensite transformation temperatures, a change in the lattice parameters, R phase formation, and angular shifts of diffraction peaks and their broadening. The largest change in the microstructure of Ti49.8Ni50.2 was provided by abc pressing to e = 1.84. Increasing the true strain to e = 9.55 resulted in a much smaller effect, suggesting that the alloy obtained a high density of structural defects even at e = 1.84. Two possible mechanisms of grain–subgrain refinement are discussed.

The aim of work is to study the effect of microstructure transformation from coarse-grained to submicrocrystalline structure in samples during warm isothermal (723K) abc-pressing on inelastic properties of Ti 49.8 Ni 50.2 (at.%) alloys. Experimental dependences of superelasticity (SE), shape memory effect (SME), the total recovered inelastic strain (SE+SME) and plastic strain versus the total shear pre-strain under torsion was obtained. It is shown that the total inelastic strain are 18% in the initial specimens, 15.8% in specimens after abc-pressing with the true strain 0.62 and monotonically increases up to 18.3% while true strain increases up to 8.44.

The results of studies of inelastic reversible strains and degree of shape recovery in samples of Ti49.3Ni50.7 (at %) alloy depending on the test temperature and phase state were presented. It is shown that high values of inelastic reversible strain in the absence of plastic deformation were observed in samples with the initial martensite structure B19′, two-phase structure B2 + B19′, and with the structure of high-temperature B2 phase. The influence of correlation of the yield stress and martensite shear stress on the manifestation of reversible inelastic strains and the development of plastic deformation was discussed.

The regularities of the change in inelastic strain in coarse-grained samples of the Ti49.3Ni50.7 (at%) alloy are studied when the samples are given torsional strain in the state of the high-temperature B2 phase. During cooling and heating, the investigated samples underwent the B2–B19′ martensite transformation (MT), the temperature of the end of the reverse MT was Af = 273 K. It was found that at the temperature of isothermal cycles “loading-unloading” Af + 8 K, when the specimen is assigned a strain of 4%, the effect of superelasticity is observed. With an increase in the torsional strain, the shape memory effect is clearly manifested. It is assumed that the stabilization of the B19′ phase in unloaded samples is due to the appearance of dislocations during deformation due to high internal stresses at the interphase boundaries of the B2 phase and the martensite phase during MT. The appearance of dislocations during the loading of samples near the temperatures of forward and reverse MT can also be facilitated by the “softening” of the elastic moduli of the alloy in this temperature range. At a test temperature above Af + 26 K, the superelasticity effect dominates in the studied samples.

The paper presents the results of studies of inelastic strains (shape memory effect (SME) and superelasticity (SE)) and plastic deformation developed under torsion in specimens of TiNi-based alloys with Ni content of 50.2 and 50.8 at. %, characterized by the initial B19′ structure of the martensite phase. It was shown that both SME (10–14%) and SE (5–6%) had been observed in plastically deformed samples of these alloys. The factors determining SE development in specimens of TiNi-based alloys with B19′ martensite structure during deformation are discussed.The paper presents the results of studies of inelastic strains (shape memory effect (SME) and superelasticity (SE)) and plastic deformation developed under torsion in specimens of TiNi-based alloys with Ni content of 50.2 and 50.8 at. %, characterized by the initial B19′ structure of the martensite phase. It was shown that both SME (10–14%) and SE (5–6%) had been observed in plastically deformed samples of these alloys. The factors determining SE development in specimens of TiNi-based alloys with B19′ martensite structure during deformation are discussed.

In the work, we studied the regularities and mechanisms of microstructure formation in binary TiNi alloys with 50.2 and 50.8 at.% Ni under warm abc pressing with a stepped decrease in strain temperature (873, 673, 623, and 573 К) and isothermal (723 К) multipass caliber rolling. In the TiNi alloy with 50.2 at.% Ni at all abc pressing stages, microstructures inhomogeneous in grain size were formed due to faster dynamic recrystallization and hence faster formation of finer grains and subgrains in strain localization bands compared to microvolumes bounded by these bands. After final abs pressing at 573 К with a total true strain е = 7.7, a microstructure composed of submicro-and nanocrystalline grains and subgrains was found. In the TiNi alloy with 50.8 at. % Ni subjected to warm rolling, three stages of grain structure evolution were revealed. At the first stage with low strains, the average grain size ‹d› increased due to collective dynamic recrystallization. At the second and third rolling stage, the average grain size ‹d› decreased steeply due to discontinuous and continuous dynamic recrystallization. On rolling at е = 2.0, a microstructure composed of micro-and submicrocrystalline grains was formed. An algorithm was proposed for estimating the critical strain for the onset of dynamic recrystallization from dependences of grain sizes on true strain. The sequences and temperatures of martensite transformations from a cubic В2 phase to rhombohedral R and monoclinic В19′ martensite phases were studied depending on the strain accumulated in abc pressing and rolling.

The paper presents experimental research results on the temperature dependence of reversible inelastic strain (superelasticity and shape memory effect) in coarse-grained Ti49.3Ni50.7 specimens (at %) under torsion. The experiments demonstrate that its value can measure up to ∼18% against minimum plastic strain accumulation in the material in martensitic and austenitic states with low martensite shear stresses.

The results of the position analysis of the yield stress &tau, 0.3 on the "stress&ndash, strain" (&tau, &ndash, &gamma, ) dependences, received at the torsion of specimens of Ti49.8Ni50.2 (at%) alloy are presented. The critical stress &tau, 0.3 (IV), corresponding to the end of linear stage III and the beginning of the intensive development of plastic strain at stage IV, preceding the fracture of the specimens, were obtained as well. The structure of the specimens was transformed from coarse-grained to microcrystalline as a result of warm (723 K) abc pressing with a true deformation e of 8.4. The regularities of the development of reversible inelastic strain (superelasticity, SE, and shape memory effect, SME) and plastic strain &gamma, pl after isothermal (295 K) loading of specimens up to &tau, &le, &tau, 0.3(IV), unloading, and their subsequent heating up to 500 K are studied. From the joint analysis of the &ldquo, &rdquo, dependences obtained at 295 K and "plastic strain&ndash, total strain" dependences the yield stress &tau, 0.3 corresponding to the development of 0.3% of the plastic strain under loading of the specimens was determined. Critical stress &tau, 0.3(IV) was determined as equal to the stress corresponding to a deviation of 0.3% from the linear &ldquo, dependence at stage III. It is shown that the yield stress &tau, 0.3 for all specimens is localized at the beginning of stage III for all specimens. The ratio &tau, 0.3(IV)/&tau, 0.3 is from 2.3 to 3.8. The accumulation of plastic strain at stage III (after loading with &tau, from &tau, 0.3 to &tau, 0.3(IV)) is from 2.4% to 4.7% (depending on the true deformation of the specimens during warm abc pressing). Thus, stage III is the stage of deformation hardening of specimens under torsion. On the basis of the results of this and previous works it is shown that, in alloys with thermoelastic martensitic transformations and with thermomechanical memory, the ratio &tau, 0.3 can vary in a wide range: in reinforced specimens &tau, 0.3 can be close to &tau, 0.3(IV), and in more ductile specimens &tau, 0.3 can be significantly less than &tau, 0.3(IV). However, in order to correctly determine the yield stress of &tau, 0.3 and the corresponding strain &gamma, t(0.3), it is necessary to carry out a joint analysis of &ldquo, and "plastic strain&ndash, total strain" dependencies.

The paper presents research data demonstrating the effect of warm caliber rolling on the martensite transformation temperatures, shape memory effect, and superelasticity in Ti49.2Ni50.8 (at %). The experimental values of inelastic strain in coarse-grained and microcrystalline Ti49.2Ni50.8 (at %) specimens exceed the theoretical limit of recoverable strain or maximum lattice strain for TiNi-based alloys.

The paper presents research results on the temperature dependence of inelastic strain recovery due to superelasticity and shape memory effects under torsion in coarse-grained and microcrystalline TiNi specimens containing 50.8 at % of Ni (Ti49.2Ni50.8 (at %)). It is found that under certain temperature and deformation conditions, the recovery strain exceeds the theoretical limit of recoverable strains or maximum lattice strain in B2↔R↔B19′ transformations. Using a special algorithm, the torsional strain is converted to its equivalent (by Mises) tensile strain. The results are compared with data obtained by other researchers.

The paper reports on a study of martensite transformation temperatures and inelastic properties of binary TiNi alloy with a Ni content of 50.8 at.% subjected to warm caliber rolling. It is shown that warm rolling makes possible micro- and submicrocrystalline structures in the TiNi specimens. The total inelastic deformation in the rolled specimens in torsion reaches 8.5%-9.5% (99% shape recovery) of which the shape memory effect is 5%-6%.

The regularities of microstructure formation in binary TiNi alloys with a Ni content of 50.2 and 50.8 at.% under warm abc pressing and isothermal (723 K) multipass caliber rolling had been studied. Microstructure composed of submicrocrystalline grains and subgrains was found after final abc pressing at 723 K with a total true strain e = 8.44. Three stages of grain structure evolution were revealed in the TiNi alloy with 50.8 at.% Ni subjected to warm rolling. At the first stage with low strains, the average grain size 〈d〉 increased due to collective dynamic recrystallization. The average grain size 〈d〉 decreased steeply due to discontinuous and continuous dynamic recrystallization at the second and third rolling stage. Microstructure composed of micro- and submicrocrystalline grains was observed after rolling with e = 2.0. The sequences and temperatures of martensite transformations from a cubic B2 phase to rhombohedral R and monoclinic B19′ martensite phases were studied in depend on the strain accumulated by samples under abc pressing and rolling.