Исследовано влияние комбинированной обработки методом ротационной ковки при комнатной температуре с последующим равноканальным угловым прессованием при 150 °C и старением на структуру, фазовые превращения и прочностные характеристики Al – Mg2Si-сплавов, легированных Sc или добавками (Sc + Zr) и (Sc + Hf ). На основании полученных результатов исследований рекомендованы режимы старения сплавов в исходном состоянии и при комбинированной обработке, обеспечивающие повышение как их прочности, так и пластичности. Наилучший комплекс механических характеристик получен у сплава Al – Mg2Si с добавкой (Sc + Hf ).

The effect of combined processing by rotary swaging at room temperature followed by equal-channel angular pressing at 150°C and subsequent aging on the structure, phase transformations and strength characteristics of Al – Mg2Si alloys with Sc and with joint additions of (Sc + Zr) and (Sc + Hf) is studied. The results obtained are used to recommend the aging modes for alloys in the initial state and after the combined processing to ensure an increase in their strength and ductility. The best set of mechanical characteristics is obtained for the Al – Mg2Si – (Sc + Hf) composition.

The microstructure, mechanical properties and corrosion resistance of promising medical Zn – 1

Исследованы микроструктура, механические свойства и коррозионная стойкость перспективных медицинских сплавов Zn – 1 % Mg – 0,1 % Dy и Zn – 1 % Mg – 0,1 % Mn после кручения под высоким давлением (КВД). Показано, что КВД способствует формированию в обоих сплавах ультрамелкозернистой структуры с размерами зерна α-Zn 450 – 700 нм, измельчению зернограничной магниевой фазы до наноразмеров и выделению частиц, богатых Mn и Dy. Такое измельчение структуры способствует одновременному росту прочности и пластичности сплавов без изменения их коррозионной стойкости. При этом скорость коррозии сплавов как до, так и после КВД не превышает 0,35 мм/год.

The microstructure, mechanical properties and corrosion resistance of promising medical Zn - 1% Mg - 0.1% Dy and Zn - 1% Mg - 0.1% Mn alloys after high-pressure torsion (HPT) are studied. It is shown that the HPT results in formation of an ultrafine-grained structure of alpha-Zn with grain size 450 - 700 nm in both alloys. The grain-boundary magnesium phase is refined to a nanosize and Mn- and Dy-enriched particles are precipitated. This refinement of the structure leads to a simultaneous increase in the strength and ductility of both alloys without changing their corrosion resistance. At the same time, the corrosion rate of the alloys both before and after the HPT does not exceed 0.35 mm/year.

The structure, aging kinetics, and mechanical properties of new Mg–Sm–Tb–Zr alloys, which are prepared by hot extrusion and differ in the content of rare-earth metals and their ratio, are studied. Samarium and terbium are found to differently affect recrystallization during deformation and the character of strengthening, which occurs in the course of additional aging for different times and results from the decomposition of a magnesium-based solid solution. The mechanical properties of the alloys subjected to hot extrusion and aging, in particular, upon heating in the temperature range up to 300°C, are determined.

This work examines the possibility of regulating the corrosion rate of Fe-Mn-Si alloys by modifying their structure via equal channel angular pressing. It is found that the formed ultrafine-grained austenitic structure of Fe-Mn-Si alloys leads to a significant increase in strength characteristics at satisfactory ductility. The presence of special twin boundaries in the structure of Fe-Mn-Si alloys improves their corrosion resistance, while a predominantly grain-subgrain structure in the absence of twin boundaries increases the corrosion rate up to 0.4 mm/year. The shape memory effect in the studied alloys manifests itself at temperatures unacceptable for medical use. Structure refinement by equal channel angular pressing in modes that ensure a completely austenitic state leads to a decrease in shape memory properties.

Prospects of development of light structural magnesium-based alloys alloyed with rare earth metals are considered. The reasons behind the highest strengthening of magnesium alloys alloyed with some rare earth metals separately or in several combinations are analyzed. The obtained experimental data are compared with published results.

The kinetics of microcracks accumulation and fracture at various stages of tension of grade 20 steel samples with coarse-grained and ultrafine-grained (UFG) structure obtained by equal-channel angular pressing (ECAP) has been studied. To research the effect of mechanical degradation, a part of the samples were subjected to preliminary cycling to a relative lifetime of 50%, followed by tensile tests, during which the parameters of acoustic emission and deformation fields obtained by digital image correlation were evaluated, and the intensity of the residual magnetic field was measured. The length and density of surface microcracks were measured by optical microscopy using computer image analysis. It is established that pre-cycling causes hardening of the material and a decrease in its plasticity. The fracture stages were revealed, and the origins of fatigue cracks were found on the internal delaminations of samples with a UFG structure after preliminary cyclic loading. It is shown that the formation of the UFG structure after the ECAP of samples made of grade 20 steel leads to hardening and reduction of the fracture work, the area of the plastic zone, maximum major deformations and damage, as well as to an increase in the number of AE signals and the intensity of the residual magnetic field.

Abstract—The effect of the microstructure of Zn–1

The effect of equal-channel angular pressing (ECAP) at 150°C and subsequent aging on the structure and strength characteristics of Al–Mg2Si alloys with scandium and joint (Sc + Zr) and (Sc + Hf) additions is studied. Hardness and electrical resistivity curves demonstrate the decomposition of the supersaturated solid solution in the alloys with (Sc + Zr) and (Sc + Hf) additions is found to be same, and the optimum aging conditions of the alloys are obtained. The microstructure of the alloys and precipitation of secondary phases are studied in detail using scanning and transmission electron microscopy (SEM and TEM, respectively). The alloys subjected to ECAP and aging demonstrate an increase in the strength and the plasticity due to compensation of aging processes by recovery processes related to restructuring a dislocation structure.

In this work, the effect of rotary swaging (RS) with a deformation degree (ε) equal to 1.28 and 2.31 on the microstructure, corrosion resistance and mechanical properties of a potential medical alloy Mg-1.1%Zn-1.7%Dy was studied. It was shown that RS at ε = 1.28 leads to a grain refinement of the studied alloy by 10 times (from ~300–400 µm to ~30–40 µm). An increase in the deformation degree up to ε = 2.31 leads to the formation of an inhomogeneous microstructure with regions containing both grains ~30–40 µm in size and zones with grains ~5–10 µm in size. Grain refinement after Rs leads to an increase in resistance to electrochemical corrosion (corrosion potential increases from -1550 ± 9 mV in the quenched state to -1442 ± 23 and -1454 ± 35 mV after RS at ε = 1.28 and ε = 2.31, respectively), but does not cause a change in the current density. But the degradation rate of the alloy increases with an increase in the deformation degree up to 3.46 ± 1.06 mm/y. The structure refinement after RS at ε = 1.28 leads to a significant increase in the strength of the alloy in comparison with the quenched state (ultimate tensile strength (UTS) increases from 70 ± 13 to 273 ± 7 MPa) with a drop in ductility from 23.1 ± 5.1 to 14.0 ± 2.9%. An increase in the deformation degree up to ε = 2.31 does not lead to an increase in the strength of the alloy (UTS = 267 ± 4 MPa), but causes an increase in ductility (δ = 21.1 ± 1.6%), apparently due to texturechanges, occurring in the alloy.

—The effect of the microstructure of Zn–1% Mg and Zn–1% Mg–0.1% Ca alloys after treatment under various conditions (casting, annealing, aging) on their mechanical and corrosion properties has been studied. The addition of calcium is shown not to degrade the strength and corrosion properties of the Zn–1% Mg alloy. The change in the microstructure of the alloys during annealing and aging significantly affect their corrosion resistance and mechanical characteristics. For example, annealing of both alloys leads to an increase in their corrosion resistance and a decrease in the ultimate tensile strength and plasticity at a simultaneous increase in the yield strength. Subsequent aging at 150°C for 1 h slightly decreases the corrosion characteristics and causes further softening of the alloys at a slight increase in their plasticity. Our results demonstrate that, for the alloys under study to be successfully used as medical materials, they should be subjected to deformation treatment in order to increase their strength and plasticity as a result of microstructural and textural transformations.

Abstract—The structure, electrical conductivity, and mechanical properties (including fatigue strength) of a Cu–0.8

The possibility of producing alloys, which are characterized by high degradation rate and used for manufacturing biodegradable implants, is studied on Fe–Mn–C alloys subjected to equal-channel angular pressing (ECAP). In particular, the attention is paid to the preparation of alloys, which have an ultrafine-grained structure and a high density of boundaries of structural elements and are in completely austenitic state. The effect of a structure on the corrosion rate, the mechanical properties, and in vitro biocompatibility has been revealed. An analysis of X-ray diffraction and transmission electron microscopy data for the alloys subjected to ECAP shows the formation of an austenitic partially or completely twin structure. The formed structure determines a high level of the strength characteristics while maintaining an adequate plasticity. As the uniformity of the twin structure and density of twin packets increases and the twin size decreases, the corrosion rate is shown to decrease. Based on results of in vitro studies of the hemolytic efficiency and cytotoxicity, the biocompatibility of the alloys subjected to ECAP is retained. The treatment conditions of samples are found not to affect their biocompatibility and to ensure a similar level of the adherence of mesenchymal cells with an osteogenic potential on the surface of the alloy samples subjected to ECAP.

—The effect of rotary swaging (RS) at a strain ε = 1.28 and 2.31 on the microstructure, corrosion resistance, and mechanical properties of a potential medical Mg–1.1% Zn–1.7% Dy alloy is studied. RS at ε = 1.28 is shown to lead to almost 10-fold grain refining (from 300–400 to 30–40 μm). An increase in the strain to ε = 2.31 leads to the formation of a nonuniform microstructure characterized by areas containing grains both 30–40 and 5–10 μm in size. The grain refining after RS results in an increase in the electrochemical corrosion resistance (corrosion potential increases from –1550 ± 9 mV, which is observed for the quenched state, to –1442 ± 23 and –1454 ± 35 mV, which correspond to the alloy subjected to RS at ε = 1.28 and 2.31, respectively) but does not cause changes in the corrosion current density. In this case, the degradation rate of the alloy increases up to 3.46 ± 1.06 mm/year as the strain increases. The structure refining observed after RS at ε = 1.28 results in a substantial increase in the strength of the alloy as compared to that of the quenched alloy (ultimate strength increases from 70 ± 13 to 273 ± 7 MPa) and a decrease in the plasticity from 23.1 ± 5.1 to 14.0 ± 2.9%. An increase in the strain to ε = 2.31 does not increase the strength of the alloy (σ u = 267 ± 4 MPa) and causes an increase in the plasticity (δ = 21.1 ± 1.6%), which is likely to result from textural changes having occurred in the alloy.

Abstract—The effect of rotary swaging (RS) at a strain ε = 1.28 and 2.31 on the microstructure, corrosion resistance, and mechanical properties of a potential medical Mg–1.1

Effect of the structure and texture caused by high pressure torsion (HPT) on mechanical properties, corrosion resistance and in vitro biocompatibility of pure Zn was studied. HPT leads to the formation of an ultrafine-grained (UFG) structure with an average grain size of 710 +/- 40 nm. In addition, a sharp basal texture is formed in pure Zn after HPT. These structure and texture features lead to an increase in the ultimate tensile strength of pure Zn by 5.5 times while the ductility grows significantly. Pure Zn in both microstructural states does not increase the hemolytic activity of red blood cells. An interesting observation is the reduction of the cytotoxicity of pure Zn after HPT, which can be associated with a slight increase in its degradation rate.