The influence of the ultrafine-grained structure formed by equal-channel angular pressing via the “Conform” scheme on the fatigue behavior of metastable β-alloy Ti-15Mo has been studied. It is shown that the alloy with a two-phase ultrafine-grained structure achieved the best mechanical properties and enhanced fatigue endurance limit (up to 710 MPa on the basis of 10⁷ cycles) due to the total contribution of grain boundary, dislocation, and phase strengthening mechanisms. A fractographic analysis of the fracture surface of samples after fatigue tests showed the features of fatigue crack propagation depending on the type of alloy microstructure. The general and distinctive features of fatigue failure of alloy samples in the initial coarse-grained (α + β)-, single-phase coarse-grained β-, and ultrafine-grained (α + β)-states are revealed. In all of the samples, a fatigue crack nucleated on the surface and propagated downward, i.e., perpendicular to the direction of the applied pressures. It is shown that fracture surfaces of the ultrafine-grained samples had a high roughness and were characterized by the presence of a large number of secondary cracks, as compared to the coarse-grained analogues.

At present, researchers pay great attention to the development of metastable β-titanium alloys. A task of current importance is the enhancement of their strength and fatigue properties. An efficient method for increasing the strength of such alloys could be severe plastic deformation. The object of this study was a medical metastable β-titanium alloy Ti-15Mo (ASTM F2066). The alloy in the (α + β) state was for the first time deformed by combined processing, including equal channel angular pressing-conform and drawing. Such processing enabled the production of long-length rods with a length of 1500 mm. The aim of the work was to study the effect of the combined processing on the alloy’s microstructure and mechanical properties. An ultrafine-grained structure with an average size of structural elements less than 100 nm was obtained. At the same time, high strength and ductility (σ_uts = 1590 MPa, δ = 10%) were achieved, which led to a record increase in the endurance limit (σ₋₁ = 710 MPa) under tension-compression terms.

Background. One of the most important tasks for modern orthopedics is the development of materials for permanent (non-removable) implants with high mechanical properties on the one hand, and high biocompatibility and bioactivity on the other hand. In the present work we propose an approach to solving this problem consisting in the formation of ultrafine-grained (UFG) structure in low-modulus pseudo-β-titanium alloy Ti-15Mo and modification of its surface by plasma electrolytic oxidation (PEO).Aim. To evaluate the influence of structure and PEO modes on the peculiarities of Ti-15Mo alloy porous coating formation, its biocompatibility and adhesion activity of mesenchymal multipotent cells.Materials and methods. The material of the study was UFG pseudo β-titanium alloy Ti-15Mo with modified surface by PEO method. To investigate the biocompatibility of uncoated and PEO-coated samples, a comparative study of their hemolytic activity and cytotoxicity in vitro was carried out. To evaluate the osteoconductivity, the stimulation of cell adhesion by the alloy samples was studied.Results. Surface modification of Ti-15Mo alloy by PEO method resulted in the formation of coatings with developed pore system. Such topography of the coatings is close to the topography of the bone tissue that increases the area of the implant/bone contact, positively influences the osteointegration of the cells – osteoblasts and reduces the terms of the implant engraftment. It is shown that the samples from UFG alloy with PEO coatings have no toxic effect on blood cells and promote adhesion of mesenchymal multipotent cells – osteoblast precursors, which can be considered as an indicator of osteoconductivity of the modified titanium alloy surface.Conclusion. The obtained results testify to the prospects of this development of bioimplants creation for the purposes of traumatology, orthopedics and oncology.

The manufacturing of personalized implants from Ti–6Al–4V alloy using additive manufacturing technologies is a promising direction in modern medicine. However, components produced by these methods are characterized by a non-equilibrium microstructure, high residual stresses, and anisotropy of mechanical properties, which necessitates subsequent heat treatment. The aim of the present work was a systematic comparative study of the effect of three heat treatment regimes—stress relief annealing (600 °C, 3 h), subtransus annealing in the (α + β) region (950 °C, 1 h, furnace cooling), and solution treatment followed by aging (STA: 950 °C, 0.5 h, water quenching + aging at 675 °C, 3 h)—on the microstructure and mechanical properties of Ti–6Al–4V alloy manufactured by laser powder bed fusion (L-PBF) and plasma arc directed energy deposition (PA-DED). The microstructure was examined using scanning electron microscopy, transmission electron microscopy, and electron backscatter diffraction (EBSD). Tensile mechanical properties were determined in two directions: parallel and perpendicular to the build direction. Stress-relief annealing led to an increase in the ductility of the alloy without a noticeable decrease in strength and without significant changes in the microstructure. Subtransus annealing resulted in the formation of an equilibrium lamellar (α + β) structure, which provided a substantial increase in ductility with a moderate decrease in strength. Solution treatment and aging resulted in formation of a bimodal microstructure. Subtransus annealing (both alloys), STA (L-PBF) and stress relief annealing (PA-DED) provided properties comparable to those of wrought material. The obtained results form the basis for a scientifically informed selection of both the manufacturing route and the heat treatment regime for biomedical implants made of Ti–6Al–4V alloy.