Biodegradable materials, which have the ability to resorb in the body, are new and promising materials for medical implants. Currently, scientists carry out the investigations according to three directions: Mg, Fe, and Zn alloys. Zinc-based alloys and zinc have good solubility in the body, which meets the clinical requirements of implants. However, pure zinc has low mechanical properties, including hardness and tensile strength. Therefore, at present, the world scientific community is seeking ways to improve the properties of pure zinc by alloying. Another known approach is the ultrafine-grained (UFG) structure formation by the severe plastic deformation (SPD) methods, which are based on the large plastic deformations under high pressure and relatively low homologous temperatures. In this work, the authors studied the influence of high pressure torsion of pure zinc with various numbers of revolutions. The paper presents calculations of shear deformation after SPD. The authors investigated the dependence of mechanical properties and microstructure on the deformation degree. Tension tests at room temperature were carried out, and microhardness was measured. The authors studied the structure using scanning electron microscopy and optics. The study identified that the use of high pressure torsion leads to an increase in the tensile strength of pure zinc up to 140 MPa and ductility up to 40 % resulting from dynamic recrystallization.

In this paper, the authors consider the mechanisms of formation of high-strength states in the Zn–1%Li–2%Mg alloy as a result of its processing by the high pressure torsion (HPT) method. For the first time, the study showed that using HPT treatment, as a result of varying the degree of deformation at room temperature, it is possible to increase the ultimate strength of a zinc alloy from 155 to 383 MPa (with an increase in the yield stress from 149 to 306 MPa) without losing its ductility. To explain the reasons for the increase in the zinc alloy mechanical properties, its microstructure was analyzed by scanning electron microscopy (SEM), X-ray phase analysis (XPA), X-ray diffraction analysis (XRD), and small-angle X-ray scattering (SAXS). Using XPA, the authors established for the first time that Zn(eutectic)+β-LiZn4(eutectic)→~LiZn3+Zn(phase)+Zn(precipitation) and MgZn2→Mg2Zn11 phase transformations occur in the zinc alloy during HPT treatment. SEM analysis showed that at the initial stages of HPT treatment, cylindrical Zn particles with a diameter of 330 nm and a length of up to 950 nm precipitate in β-LiZn3 phase. At the same time, the SAXS method showed that needle-like LiZn4 particles with a diameter of 9 nm and a length of 28 nm precipitate in the Zn phase. The study established that, only spherical Zn and LiZn4 particles precipitate at high degrees of HPT treatment. Precision analysis of the zinc alloy microstructure showed that HPT treatment leads to grain refinement, an increase in the magnitude of crystal lattice microdistortion, a growth of the density of dislocations, which are predominantly of the edge type. As a result of the analysis of hardening mechanisms, the authors concluded that the increase in the zinc alloy strength characteristics mainly occurs due to grain-boundary, dislocation, and dispersion hardening.

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It is known that zinc biodegradable alloys are a promising material for producing biomedical implants for orthopedics and vascular stents. Among them, the Zn-Ag-Cu zinc alloy is of special interest due to the antibacterial and antimicrobial properties of Ag and Cu. To improve the mechanical properties of the Zn-4Ag-1Cu zinc alloy, the effect of equal-channel angular pressing (ECAP) on the microstructure and strength has been investigated. The ECAP conditions for the Zn-4Ag-1Cu alloy were chosen by modeling in the Deform 3 D program (temperature and strain rate). The microstructure was analyzed using transmission electron microscopy, scanning electron microscopy and X-ray diffraction analysis. The study of strength was carried out by measuring the microhardness and tensile tests of small samples with a gauge dimension of 0.8 × 1 × 4 mm3. The microstructure after ECAP was characterized by equiaxed grains ranging in a size from 1.5 µm to 4 µm with particles in a size from 200 nm to 1 µm uniformly distributed along the boundaries. The ECAP samples showed a high strength of 348 MPa and good ductility of up to 30%, demonstrating their great potential as promising materials for producing medical stents.