Search

Abstract: Microstructure, mechanical and corrosion properties of binary magnesium–dysprosium (Mg-5, 10, 15, 20wt.% Dy) alloys were investigated for medical applications. In the as-cast condition, the distribution of Dy is quite inhomogeneous. Mg–10Dy alloy exhibits a moderate tensile and compression yield strength, and the best elongation and corrosion resistance. After T4 (solutionizing) treatment, the distribution of Dy becomes homogeneous. The tensile and compression yield strength of all Mg–Dy alloys decreases. The elongation remains unchanged, while the corrosion resistance is largely improved after T4 treatment. [Copyright &y& Elsevier]

Abstract: The biocorrosion behavior of a magnesium alloy in two simulated body solutions, Hank''s solution and simulated blood plasma (SBP) solution was investigated by electrochemical and weight loss testing for biomedical application. The solution volume/surface area (SV/SA) ratio was changed to reveal the effect of immersion condition on the biocorrosion behavior. A same tendency was observed in the corrosion rate of magnesium alloy in all testing conditions: a high corrosion rate at the initial stage, and rapid decrease in the first 2–3 days followed by a stable corrosion rate in the following stage. A higher corrosion rate was observed in Hank''s solution than in SBP solution due to high Cl−, low Ca2+ and PO4 3− concentration in Hank''s solution. However, no difference in the surface reaction product was observed between the samples immersed in Hank''s solution and in SBP solution. It was found that the SV/SA ratio significantly affected the corrosion rate of magnesium alloy. Low ratio resulted in a high pH, which resisted the corrosion. But when the ratio was high enough, 6.7 for example, the influence was negligible. By changing the ratio, the biocorrosion behavior of magnesium implant in different implantation sites can be simulated, for example, low ratio for the case of in muscle and high ratio for the case of in marrow cavity. It is suggested that selection of the simulated solution and the SV/SA ratio would be very necessary to simulate different the in-vivo biodegradation behavior of magnesium in different implantation environment. [Copyright &y& Elsevier]

• Porous Ag-enriched phase forms during corrosion via de-alloying of Mg-Ag phase. • Dissolved Ag mainly redeposits to Mg surface forming Ag nanoparticles. • Both of the formed porous Ag-enriched phase and re-deposited Ag nanoparticles can result in evident cathodic activation. • The cathodic activation ability is significantly affected by Ag content and existing form of Ag. The effect of Ag on cathodic activation and corrosion behaviour of Mg-Mn-Ag alloys are investigated in the present work. During corrosion, Mg-Ag intermetallic phase undergoes dealloying to form porous Ag-rich remnant whereas Ag in the alloy matrix is dissolved to form Ag+ ions that subsequently redeposit on the alloy surface via displacement reaction with Mg to form Ag nanoparticles, which lead to significant cathodic activation. The cathodic activation is a self-catalysed process since enhanced cathodic activity promotes anodic dissolution which, consequently, results in further enhancement of cathodic activity. Thus, the corrosion rate of Mg-2 Mn-4Ag alloy increases significantly with immersion time. [ABSTRACT FROM AUTHOR]

Abstract: Microstructure, biocorrosion behavior and cytotoxicity of an as-extruded Mg–11.3Gd–2.5Zn–0.7Zr (wt%) alloy were studied, in order to develop new biodegradable magnesium alloy. The microstructure of the as-extruded alloy mainly consists of the refinement grains, a lamellar X phase with the 14H-type long period stacking ordered (LPSO) structure in grain boundaries and the 14H-type LPSO structure within initial grains and refinement grains, and a small amount of β phase. The as-extruded alloy has high strength at room temperature. The corrosion rate in Hanks'' solution is only 0.17mm/year and the corrosion mode of the alloy is uniform corrosion, which is much better than that of as-extruded Mg–10.2Gd–3.3Y–0.6Zr (wt%) alloy. Moreover, the cell toxicity grade of the Mg–11.3Gd–2.5Zn–0.7Zr alloy is Grade 1, indicating only slightly having cytotoxicity. The desired results indicate the Mg–Gd–Zn–Zr alloy with LPSO structure will become one of novel promising high-strength biodegradable magnesium alloys. [Copyright &y& Elsevier]

Abstract: Mn and Zn were selected to develop a Mg–Zn–Mn magnesium alloy for biomedical application due to the good biocompatibility of Zn and Mn elements. Microstructure, mechanical properties, corrosion properties and biocompatibility of the Mg–Zn–Mn alloys have been investigated by use of optical microscope, scanning electron microscope, tensile testing, and blood hemolysis and cell toxicity. Microstructure observation has shown that the addition of Zn and the extrusion significantly refined the grain size of both the as-cast and the extruded magnesium alloys, which mainly contributes to the high tensile strength and good elongation. Polarization test has shown Zn could accelerate the formation of a passivation film, which provides good protection to the magnesium alloy against simulate body fluid. Cell culture and hemolysis tests have shown that the magnesium alloy did not have cell toxicity, showing good cytocompatibility, but the alloy caused hemolysis to blood system. It was suggested that surface modification have to be adopted to improve the blood compatibility of the magnesium alloy for the application in blood environment. [Copyright &y& Elsevier]