In the field of magnesium-based degradable implantable devices, the Mg-Y-RE-Zr alloying system (WE-type) has gained popularity due to its satisfying degradation rate together with mechanical strength. However, utilization of RE and Zr in the WE-type alloys was originally driven to improve Mg-based alloys for high-temperature applications in the industry, while for medical purposes, there is a question of whether the amount of alloying elements may be further optimized. For this reason, our paper presents the Mg-3Y (W3) magnesium alloy as an alternative to the WE43 alloy. This study shows that the omission of RE and Zr elements did not compromise the corrosion resistance and the degradation rate of the W3 alloy when compared with the WE43 alloy; appropriate biocompatibility was preserved as well. It was shown that the decrease in the mechanical strength caused by the omission of RE and Zr from the WE43 alloy could be compensated for by severe plastic deformation, as achieved in this study, by equal channel angular pressing. Ultrafine-grained W3 alloy exhibited compression yield strength of 362 ± 6 MPa and plastic deformation at maximum stress of 18 ± 1%. Overall, the early results of this study put forward the motion of avoiding RE elements and Zr in magnesium alloy as a suitable material for biodegradable applications and showed that solo alloying of yttrium is sufficient for maintaining desirable properties of the material at once.

• Klíčová slova
• corrosion rate, magnesium, mechanical properties, ultrafine-grain microstructure, yttrium,
• Publikační typ
• časopisecké články MeSH

This work was focused on revealing the relation between the microstructure and corrosion dynamics in dilute Mg97.94Zn0.56Y1.5 (at.%) alloys prepared by the consolidation of rapidly solidified (RS) ribbons. The dynamics of the corrosion were followed by common electrochemical methods and the acoustic emission (AE) technique. AE monitoring offers instantaneous feedback on changes in the dynamics and mode of the corrosion. In contrast, the electrochemical measurements were performed on the specimens, which had already been immersed in the solution for a pre-defined time. Thus, some short-term corrosion processes could remain undiscovered. Obtained results were completed by scanning electron microscopy, including analysis of a cross-section of the corrosion layer. It was shown that the internal strain distribution, the grain morphology, and the distribution of the secondary phases play a significant role in the corrosion. The alloys are characterized by a complex microstructure with elongated worked and dynamically recrystallized α-Mg grains with an average grain size of 900 nm. Moreover, the Zn- and Y-rich stacking faults (SFs) were dispersed in the grain interior. In the alloy consolidated at a lower extrusion speed, the homogeneous internal strain distribution led to uniform corrosion with a rate of 2 mm/year and a low hydrogen release. The consolidation at a higher extrusion speed resulted in the formation of uneven distribution of internal strains with remaining high strain levels in non-recrystallized grains, leading to inhomogeneous growth and breakdown of the corrosion layers. Therefore, homogeneity of the internal strain distribution is of key importance for the uniform formation of a protective layer.

• Klíčová slova
• acoustic emission, corrosion properties, magnesium alloys, microstructure, rapid solidification,
• Publikační typ
• časopisecké články MeSH

In vitro cytotoxicity testing is an indispensable part of the development of new biomaterials. However, the standard ISO 10993-5 enables variability in the testing conditions, which makes the results of the test incomparable. We studied the influence of media composition on the results of the cytotoxicity test. Solutions of ZnCl2 served as simulated extracts and we also used extracts of three types of Zn-based and Mg-based degradable metals. We incubated the cells with the solutions prepared in two types of media with two concentrations of serum (5 and 10%). We compared the toxic effect of the extracts on L929 murine fibroblast-derived cell line, which is recommended by ISO standard and on "osteoblast-like cells" U-2 OS. We also compared two methods of exposition: solutions were added either to a sub-confluent layer or to the cell suspension. We evaluated the metabolic activity of the cells using the resazurin test. We found out that in vitro cytotoxicity is dramatically influenced by the concentration of serum and by the type of the medium as well as by the type of exposition and type of cells. Therefore, when performing in vitro cytotoxicity testing of biomaterials, the authors should carefully specify the conditions of the test and comparison of different studies should be carried out with caution.

• MeSH
• biokompatibilní materiály farmakologie   MeSH
• komplexní sloučeniny farmakologie   MeSH
• kultivované buňky MeSH
• myši MeSH
• slitiny MeSH
• techniky in vitro MeSH
• testování materiálů MeSH
• viabilita buněk účinky léků   MeSH
• zvířata MeSH
• Check Tag
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• biokompatibilní materiály MeSH
• komplexní sloučeniny MeSH
• slitiny MeSH

The deformation behavior of extruded Mg alloys with a Ca or Nd addition (up to 0.5 wt.%) is addressed with respect to a specified thermo-mechanical treatment, realized by pre-compression and subsequent heat treatment at intermediate temperature. The twinning-detwinning process is discussed with respect to the initial texture and applied heat treatment. Isothermal aging leads to precipitation and segregation along twin boundaries and dislocations in the pre-compressed Mg alloys, and, thus, variation in the mobility of twin boundaries (TB) is observed in the investigated alloys. Despite individual scenarios of TB mobility in particular grains, in general, the same TB mobility modes are observed in the alloys independently on Ca or Nd alloying. The microstructure development, particularly the twin volume fraction and the mobility of tensile {10-12} twin boundaries, is tracked using scanning electron microscopy, including backscattered electron (BSE) imaging and electron backscatter diffraction (EBSD) mapping.

• Klíčová slova
• detwinning, magnesium alloys, precipitation, twin boundaries, twinning,
• Publikační typ
• časopisecké články MeSH

The impact of precompression, thermal treatment and its combination on the deformation behaviour of an extruded Mg-Zn-Ca (ZX10) alloy was studied with respect to a varied average grain size. The Hall-Petch plot was used to highlight the impact in a wide grain size interval. The initial texture of the wrought alloy was characterized by X-ray diffraction. Moreover, the evolution of microstructure and texture was provided by the electron backscatter diffraction (EBSD) technique. The obtained results indicate the strong contribution of deformation-thermal treatment on the resulting deformation behaviour. Particularly, after precompression and heat treatment, higher strengthening effect was observed in the reversed tensile loaded compared to compressed samples without any change in the Hall-Petch slope throughout the grain size interval. Unlike this strengthening effect, a reversed tension-compression yield asymmetry with higher strength values in compression has been obtained.

• Klíčová slova
• Hall–Petch relationship, Mg alloy, deformation-thermal treatment, yield asymmetry,
• Publikační typ
• časopisecké články MeSH