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The influence of Y on the microstructure, phase composition and mechanical properties of the extruded Mg-6Zn- xY-0.6Zr ( x = 0, 1, 2, 3 and 4, in wt%) alloys has been investigated and compared by optical microscopy, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectrometer and tensile testing. The increase in Y content has shown grain refinement effects on the microstructure morphologies of the extruded alloys. However, when the content of Y exceeds 2.2 wt%, the grain refinement effect of the Y is not obvious any more with the increase of the Y content. The quasicrystal I-phase (Mg3Y2Zn3), face-centred cubic structure W-phase (Mg3Y2Zn3) and a long period stacking ordered (LPSO) X-phase (Mg12YZn) can precipitate in different ranges of Y/Zn ratio (in at.%) when the Y content in the Mg-Zn-Y-Zr alloys is varied. Comparison of the mechanical properties of the alloys showed that the different ternary Mg-Zn-Y phases have different strengthening and toughening effects on the Mg-Zn-Y-Zr alloys in the following order: X-phase > I-phase > W-phase > MgZn. [ABSTRACT FROM AUTHOR]

Abstract: The effects of Mn substitution for Mg on the microstructure, mechanical properties, and corrosion behavior of Mg69−xZn27Ca4Mnx (x=0, 0.5 and 1at.%) alloys were investigated using X-ray diffraction, compressive tests, electrochemical treatments, and immersion tests, respectively. Microstructural observations showed that the Mg69Zn27Ca4 alloy was mainly amorphous. The addition of Mn decreases the glass-forming ability, which results in a decreased strength from 545MPa to 364MPa. However, this strength is still suitable for implant application. Polarization and immersion tests in the simulated body fluid at 37°C revealed that the Mn-doped Mg–Zn–Ca alloys have significantly higher corrosion resistance than traditional ZK60 and pure Mg alloys. Cytotoxicity test showed that cell viabilities of osteoblasts cultured with Mn-doped Mg–Zn–Ca alloys extracts were higher than that of pure Mg. Mg68.5Zn27Ca4Mn0.5 exhibits the highest bio-corrosion resistance, biocompatibility and has desirable mechanical properties, which could suggest to be used as biomedical materials in the future. [Copyright &y& Elsevier]