Coexistence of Intermetallic Complexions and Bulk Particles in Grain Boundaries in the ZEK100 Alloy

Magnesium-based alloys are highly sought after in the industry due to their lightweight and reliable strength. However, the hexagonal crystal structure of magnesium results in the mechanical properties’ anisotropy. This anisotropy is effectively addressed by alloying magnesium with elements like zirconium, zinc, and rare earth metals (REM). The addition of these elements promotes rapid seed formation, yielding small grains with a uniform orientation distribution, thereby reducing anisotropy. Despite these benefits, the formation of intermetallic phases (IP) containing Zn, Zr, and REM within the microstructure can be a concern. Some of these IP phases can be exceedingly hard and brittle, thus weakening the material by providing easy pathways for crack propagation along grain boundaries (GBs). This issue becomes particularly significant if intermetallic phases form continuous layers along the entire GB between two neighboring GB triple junctions, a phenomenon known as complete GB wetting. To mitigate the risks associated with complete GB wetting and prevent the weakening of the alloy’s structure, understanding the potential occurrence of a GB wetting phase transition and how to control continuous GB layers of IP phases becomes crucial. In the investigation of a commercial magnesium alloy, ZEK100, the GB wetting phase transition (i.e., between complete and partial GB wetting) was successfully studied and confirmed. Notably, complete GB wetting was observed at temperatures near the liquidus point of the alloy. However, at lower temperatures, a coexistence of a nano-scaled precipitate film and bulk particles with nonzero contact angles within the same GB was observed. This insight into the wetting transition characteristics holds potential to expand the range of applications for the present alloy in the industry. By understanding and controlling GB wetting phenomena, the alloy’s mechanical properties and structural integrity can be enhanced, paving the way for its wider utilization in various industrial applications

The Keap1/Nrf2/ARE system activators do not increase cardiac resistance to long-term ischemia/reperfusion

Oxidative stress is an important mechanism of myocardial damage during ischemia/reperfusion. To investigate the possibility of restoring the redox balance using "indirect" antioxidant effects, the cardioprotective effect Keap1/Nrf2/ARE system inducers was studied in long-term ischemia/reperfusion in vivo. Material and methods. We used the original synthetic hydrophilic monophenol sodium 3-(3'-tert-butyl-4'-hydroxyphenyl)propyl thiosulfonate (TS-13) and reference drug tert-butylhydroquinone (tBHQ). Male Wistar rats received 100 mg/kg of TS-13 solution (with drinking water) or tBHQ (intraperitoneally) daily for 7 days. Animals of the comparison groups received the corresponding solvents. Local ischemia (45 min, occlusion of the left coronary artery) and reperfusion (120 min) of the heart were simulated in vivo 1 day after last drug administration. The ECG was recorded during ischemia and reperfusion; at the end of reperfusion, the heart was removed, the zone of hypoperfusion and the zone of necrosis were detected. Changes in the expression of the mRNA of Nfe2l2, Nqo1, Hmox1, Gstp1, Rela, and Nfkb2 gene in myocardial tissue were determined by real-time TaqMan PCR. Results and discussion. Pretreatment with TS-13 and tBHQ did not influence the infarct size and the incidence of ventricular arrhythmias. Preliminary administration of tBHQ did not change the genes expression of the studied in myocardial tissue after prolonged I/R. TS-13 administration was accompanied by an increase in the content of the transcripts of the gene that encodes Nrf2 (by 7.64 times) and Nrf2-driven genes Nqo1 (by 6.46 times) and Hmox1 (by 3.63 times); the expression of the Gstp1, Rela, and Nfkb2 genes did not differ from the corresponding values of the control group; compared to animals treated with tBHQ, the expression of the Nfe2l2, Nqo1, Hmox1, Rela, and Nfkb2 genes was 16.23, 4.44, 2.68, 3.17, and 2.64 times higher, respectively. The results obtained cast doubt on the therapeutic importance of the induction of the Keap1/Nrf2/ARE system during prolonged heart ischemia/reperfusion

In vitro models for the study of Zika virus

Due to the globalization, increased trade and migration flows the probability of outbreaks of Zika fever is significantly increasing worldwide, including Black sea coast of the Caucasus in the Russian Federation. Zika fever tends to spread rapidly and to expand its geography, so the study of this virus remains an urgent task. The accumulated knowledge recently has contributed to a comprehensive study of Zika virus, but so far many questions of etiology, epidemiology, clinic, specific diagnosis and prevention remain unresolved. This review is based mainly on publications by foreign authors and leading international organizations dedicated to the study of Zika virus in the cell lines of various sources . The review summarizes recent experimental data on the use of cell lines as target cells for the study of Zika virus, their advantages and disadvantages, and the susceptibility of different cell lines to this virus. Information from bibliographic and abstract scientific databases, search websites, and publishers: RSCI, Web of Science, Scopus, MEDLINE, Google Scholar, PubMed, Springer Nature, Elsevier, and others was used in the preparation of the review

Grain Boundary Wetting Transition in the Mg-Based ZEK 100 Alloy

Modern magnesium-based alloys are broadly used in various industries as well as for biodegradable medical implants due to their exceptional combination of light weight, strength, and plasticity. The studied ZEK100 alloy had a nominal composition of 1 wt.% zinc, 0.1 wt.% zirconium, and 0.1 wt.% rare earth metals (REMs) such as Y, Ce, Nd, and La, with the remainder being Mg. It has been observed that between the solidus (Ts = 529.5 ± 0.5 °C) and liquidus temperature (Tl = 645 ± 5 °C), the Mg/Mg grain boundaries can contain either the droplets of a melt (incomplete or partial wetting) or the continuous liquid layers separating the abutting Mg grains (complete wetting). With the temperature increasing from Ts to Tl, the transformation proceeds from incomplete to complete grain boundary wetting. Below 565 °C, all grain boundaries are partially wetted by the melt. Above 565 °C, the completely wetted Mg/Mg grain boundaries appear. Their portion grows quickly with an increasing temperature until reaching 100% at 622 °C. Above 622 °C, all the solid Mg grains are completely surrounded by the melt. After rapid solidification, the REM-rich melt forms brittle intermetallic compounds. The compression strength as well as the compression yield strength parameter σ02 strongly depend on the morphology of the grain boundary layers. If the hard and brittle intermetallic phase has the shape of separated particles (partial wetting), the overall compression strength is about 341 MPa and σ02 = 101 MPa. If the polycrystal contains the continous intergarnular layers of the brittle intermetallic phase (complete wetting), the overall compression strength drops to 247 Mpa and σ02 to 40 Mpa. We for the first time observed, therefore, that the grain boundary wetting phenomena can strongly influence the mechanical properties of a polycrystal. Therefore, grain boundary wetting can be used for tailoring the behavior of materials

Coexistence of Intermetallic Complexions and Bulk Particles in Grain Boundaries in the ZEK100 Alloy

Magnesium-based alloys are highly sought after in the industry due to their lightweight and reliable strength. However, the hexagonal crystal structure of magnesium results in the mechanical properties’ anisotropy. This anisotropy is effectively addressed by alloying magnesium with elements like zirconium, zinc, and rare earth metals (REM). The addition of these elements promotes rapid seed formation, yielding small grains with a uniform orientation distribution, thereby reducing anisotropy. Despite these benefits, the formation of intermetallic phases (IP) containing Zn, Zr, and REM within the microstructure can be a concern. Some of these IP phases can be exceedingly hard and brittle, thus weakening the material by providing easy pathways for crack propagation along grain boundaries (GBs). This issue becomes particularly significant if intermetallic phases form continuous layers along the entire GB between two neighboring GB triple junctions, a phenomenon known as complete GB wetting. To mitigate the risks associated with complete GB wetting and prevent the weakening of the alloy’s structure, understanding the potential occurrence of a GB wetting phase transition and how to control continuous GB layers of IP phases becomes crucial. In the investigation of a commercial magnesium alloy, ZEK100, the GB wetting phase transition (i.e., between complete and partial GB wetting) was successfully studied and confirmed. Notably, complete GB wetting was observed at temperatures near the liquidus point of the alloy. However, at lower temperatures, a coexistence of a nano-scaled precipitate film and bulk particles with nonzero contact angles within the same GB was observed. This insight into the wetting transition characteristics holds potential to expand the range of applications for the present alloy in the industry. By understanding and controlling GB wetting phenomena, the alloy’s mechanical properties and structural integrity can be enhanced, paving the way for its wider utilization in various industrial applications