Alexei Georgievich Kolmakov

The physicomechanical properties of a skeleton composite based on carbon-graphite AG-1500 impregnated with aluminum alloys were investigated after preliminary electroplating of copper or nickel onto the surfaces of the open pores. To improve impregnation of the carbon-graphite by an autoclave-free technique, coatings that form the eutectic with aluminum were used. Investigation of the effect of impregnation temperature showed that increasing the impregnation temperature with AK12 alloy to 750°C led to filling of 43.57% of the open pores of the carbon-graphite pre-plated with copper, while for nickel-plated samples this value was 37.32%. With a further increase of the temperature to 800°C, pore filling increased to 72.27% for the copper-preplated samples and to 66.25% for the nickel-plated samples. Using an Al–Mg–Zn–Cu alloy at an impregnation temperature of 750°C, pore filling of the pre-coppered samples reached 56.87%, and of the pre-nickel-plated carbon-graphite samples 49.25%. It was found experimentally that the copper coating is more effective at improving infiltration of the matrix aluminum alloys than the nickel coating. Analysis of the chemical composition of carbon-graphite impregnated with the Al–Mg–Zn–Cu alloy revealed chemical inhomogeneity of the metal alloy composition in the pores, manifested as segregation of the more active elements (magnesium, zinc) of the matrix alloy toward the interfacial zone with the carbon-graphite. It was established that with increasing degree of pore filling by the matrix alloy, the physicomechanical properties increase (compressive and flexural strength, wear resistance, and specific electrical resistivity of the composite).

The effect of rotary swaging (RS) at room temperature and subsequent annealing at 350 °C on the microstructure, mechanical properties, and fatigue strength of Cu–35.8%Zn two-phase brass was studied. A structure with grains of α and β′ phases elongated along the deformation direction was formed after RS. It was also shown that subgrains of 200–300 nm in size, shear bands 100–200 nm wide, and deformation twins 10–30 nm wide were formed inside the α-phase grains. RS caused the increase in the yield stress (YS) from 93 ± 4 to 717 ± 6 MPa and the ultimate tensile strength (UTS) from 332 ± 2 to 744 ± 19 MPa with a decrease in ductility (El) from 71.0 ± 2.0 to 10.3 ± 1.7%. The fatigue limit also increased from 240 to 415 MPa after RS. Subsequent annealing at 350 °C induced recrystallization of the α-phase with the formation of equiaxed grains 2.2–3.6 µm in size, which resulted in a decrease in UTS to 462–466 MPa and an increase in ductility to 44–45%. Extending the annealing time to 4 h did not affect the strength and ductility values of the alloy.

The research described in this article is a continuation of a series of studies on biocompatible materials, focused on finding the optimal alloy composition and heat treatment regimes. The use of materials with a low Young’s modulus ensures the long-term safety of the implant by reducing the stress shielding effect, which causes bone resorption. This work investigates the effect of alloying with niobium in the range of (8–10) at. % on the Ti-38Zr alloy, specifically its structure, mechanical properties, Young’s modulus, and superelasticity. In this study, plates of the Ti-38Zr-(8-10)Nb (at. %) alloy were investigated after quenching and subsequent annealing. In Ti-38Zr-(8-10)Nb alloys, quenching from 600 °C fixes the β-phase of Ti. In alloys with (8-9)Nb, this is a metastable β-phase, as evidenced by its superelastic behavior under cyclic tension. Annealing at 400 °C leads to a clear decomposition of the quenched high-temperature β-phase in Ti-38Zr-(8-9)Nb alloys into β- and α′-phases. Based on the mechanical test results, it can be inferred that the precipitation of the brittle ω-phase and the α′-phase occur concurrently, since annealing at 400 °C causes a pronounced embrittlement of the Ti-38Zr-(8–9)Nb alloys (with elongation dropping from ~15% to 0.7–2.5%, respectively) alongside a substantial increase in strength (from 500 MPa to 1010 MPa). For the Ti-38Zr-10Nb alloy, the ductility also declines but remains within acceptable limits (from ~14% to ~10%), while the strength rises from 520 MPa to 630 MPa. The Young’s modulus of the Ti-38Zr-(8-10)Nb alloy after quenching is ~80 GPa. After annealing, it increases to 95 GPa for alloys with (8-9)Nb, while for 10Nb it remains at approximately 80 GPa.

—The effect of irradiation with pulsed helium ion beams and helium plasma on the structural characteristics and mechanical properties of titanium alloys with the following compositions (wt %): Ti–0.5 Nb–0.5 Mo–3 Zr–3 Al; Ti–1 Nb–1 Mo–3 Zr–3 Al; and Ti–1.5 Nb–1.5 Mo–3 Zr–3 Al was investigated. The irradiation was carried out using a Plasma Focus type device with power flux densities of q = 2 × 10⁸ W/cm² for helium ions and q = 4 × 10⁷ W/cm² for helium plasma, with pulse durations of 20–100 ns. Metallographic and X-ray phase analyses were performed and the mechanical properties (ultimate strength, yield strength, and elongation) and microhardness of the alloy samples before and after irradiation were determined. The irradiation caused a slight (less than 10%) decrease in the strength and plasticity indicators of the alloy samples, while the microhardness remained practically unchanged.

In today's world, environmental issues are becoming more and more pressing. The manufacture of structural materials such as metals, concrete, ceramics, and composites has a considerable impact on the environment. Therefore, the development and improvement of methods that minimize the adverse environmental impact and design of more sustainable production processes are fairly relevant. Currently, the concept of nature-inspired materials has been elaborated. A number of such materials have been already developed and some are being developed now. This review addresses, for the first time, the current state of research in the development of nature-inspired and safe materials based on titanium alloys and steels. The bibliography includes 144 references.

Hip joint implants are among the most prevalent types of medical implants utilized for the replacement of damaged joints. The utilization of modern implant materials, such as cobalt–chromium alloys, stainless steel, titanium, and other titanium alloys, is accompanied by challenges, including the toxicity of certain elements (e.g., aluminum, vanadium, nickel) and excessive Young’s modulus, which adversely impact biomechanical compatibility. A mismatch between the stiffness of the implant material and the bone tissue, known as stress shielding, can lead to adverse outcomes such as bone resorption and implant loosening. Recent studies have shifted the focus to β-titanium alloys due to their exceptional biocompatibility, corrosion resistance, and low Young’s modulus, which is close to the Young’s modulus of bone tissue (10–30 GPa). In this study, the microstructure, mechanical properties, and phase stability of the Ti-38Zr-11Nb alloy were investigated. Energy dispersion spectrometry was employed to confirm the homogeneous distribution of Ti, Zr, and Nb in the alloy. A subsequent microstructural analysis revealed the presence of elongated β-grains subsequent to rolling and quenching. Furthermore, grinding contributed to the process of recrystallization and the formation of subgrains. X-ray diffraction analysis confirmed the presence of a stable β-phase under any heat treatment conditions, which can be explained by the use of Nb as a β-stabilizer and Zr as a neutral element with a weak β-stabilizing effect in the presence of other β-stabilizers. Furthermore, the modulus of elasticity, as determined by tensile testing, exhibited a decline from 85 GPa to 81 GPa after annealing. Mechanical tests demonstrated a substantial enhancement in tensile strength (from 529 MPa to 628 MPa) concurrent with a 32% reduction in elongation to fracture of the samples. These alterations are attributed to microstructural transformations, including the formation of subgrains and the rearrangement of dislocations. This study’s findings suggest that the Ti-38Zr-11Nb alloy has potential as a material of choice due to its lower Young’s modulus compared to traditional materials and its stable β-phase, which enhances the implant’s durability and reduces the risk of brittle phases forming over time. This study demonstrates that the corrosion resistance of titanium grade 2 and Ti-38Zr-11Nb is comparable. The material in question exhibited no evidence of cytotoxic activity in the context of mammalian cells.

Influence of six types of blasting and electrolytic-plasma polishing on the surface roughness and wettability and interaction with the bacterium Escherichia coli of two commercial titanium-based alloys used in medicine, VT1-0 (pure titanium) and VT6 (titanium alloy with aluminum and vanadium), as well as the Ti–Nb–Zr alloy being developed at the Baikov Institute of Metallurgy and Materials Science of the Russian Academy of Sciences (IMET RAS), was studied. It was noted that all the obtained surfaces are wettable; the wetting angle is naturally the higher, the lower the surface roughness; however, in the case of all materials after sand blasting with mixtures with a wide range of particle sizes, an increase in the wetting angle is noted. All metal samples do not have antibacterial activity and do not contribute to the formation of a sterile zone. The ability to form biofilms from the bacterium E. coli on the surface of metals was studied. It was shown that their number is significantly less in the presence of samples compared to the control. The developed Ti–Nb–Zr alloy, which potentially has better biomechanical compatibility than the commercial ones used, showed no deterioration in surface characteristics and no effect on bacterial growth.

—The structure and mechanical properties (under static and fatigue loading) of Al–6.7Mg–0.3Sc–0.25Zr alloy samples synthesized by selective laser melting (SLM) horizontally and vertically relative to a build platform and subsequently aged at 360°C for 5 h are studied. The density of the synthesized samples is found to be maximal (99.88%) at a laser power of 800 W and a scanning speed of 1500 mm/s. The mechanical properties of such samples are almost independent of the build direction and are as follows: the ultimate tensile strength is σ_u = 420–430 MPa; the relative elongation, δ = 5–8%; and the fatigue limit, σ_R = 130–140 MPa.

Hip joint implants are one of the most common types of medical implants used to replace a damaged joint and restore its functional activity. Hundreds of thousands of surgeries are performed annually to install them, which underscores the importance of developing and improving materials for such implants. Modern materials for implants, including co-balt-chromium alloys, stainless steel, titanium and other titanium alloys, face problems such as the toxicity of certain elements (for example, aluminum, vanadium, nickel) and excessive Young's modulus, which negatively affects biomechanical compatibility. A mismatch between the stiffness of the implant material and the bone tissue, called stress shielding, can lead to bone resorption and loosening of the implant. Recent studies have shifted the focus to β-titanium alloys due to their exceptional biocompatibility, corrosion resistance, and low Young's modulus, which is close to the Young's modulus of bone tis-sue (10-30 GPa). Among them, Ti-38Zr-11Nb alloy is promising for use as an implant material. In this study, the microstructure, mechanical properties, and phase stability of Ti-38Zr-11Nb alloy were studied. Energy dispersion spectrometry confirmed the homo-geneous distribution of Ti, Zr, and Nb in the alloy. Microstructural analysis revealed elongated β-grains after rolling and quenching, and grinding contributed to recrystalliza-tion and the formation of subgrains. X-ray diffraction analysis confirmed the presence of a stable β-phase under any heat treatment conditions, which is explained by the use of Nb as a β-stabilizer and Zr as a neutral element with a weak β-stabilizing effect in the pres-ence of other β-stabilizers. The modulus of elasticity after annealing decreased from 85 GPa to 81 GPa. Mechanical tests showed a significant increase in tensile strength (from 529 MPa to 628 MPa) simultaneously with a 32% decrease in elongation to fracture of the samples. These changes are caused by microstructural transformations such as the for-mation of subgrains and rearrangement of dislocations. Based on the results of the study, it can be concluded that Ti-38Zr-11Nb alloy is a promising material due to its lower low Young's modulus relative to the classical materials used and stable β-phase, which pro-vides the possibility of long-term use of the implant, without the risk of formation of brittle phases.

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