The microstructure evolution and mechanical properties improvement of the AZ61 alloy by adding Sc

The improvement of mechanical properties and the microstructure evolution through adding Sc to AZ61magnesium alloy were studied. The results indicated that the Mg17Al12 phase in the extruded AZ61 alloy was mainly distributed around the sub-structured and fine deformed grains, resulting in the nonuniform microstructure. The addition of Sc could effectively suppress the band-like precipitation of Mg17Al12 phase and improve the uniformity of microstructure. The grain sizes of the extruded alloys showed a trend of first decreasing and then increasing with the increase of Sc, which was mainly attributed to the secondary phase. The AZ61-0.5Sc alloy exhibited the best mechanical properties, its ultimate tensile strength and yield strength were 14.8MPa and 40.8MPa higher than those of the extruded AZ61 alloy, respectively, which was ascribed to the fine grains and abundant secondary phase in the alloy.

Effects of Ce-Rich Misch Metal on the Microstructures and Tensile Properties of as-Cast Mg-7Al-3Sn-1Zn Alloys

The effects of small amounts of Ce-rich misch metal (Mm: 0.5, 1.0 and 2.0 wt.%) addition on the microstructure and tensile properties of as-cast Mg-7Al-3Sn-1Zn wt.% (ATZ731) alloy have been investigated. The addition of Mm restricts the formation of the Mg17Al12 phase but greatly promotes the Al4Mm phase. The proper Mm addition enhances the strength and ductility of ATZ731 alloys at both room temperature (RT) and 175 °C. ATZ731 alloys with 1.0 wt.% Mm addition exhibit an advantageous combination strength and ductility, with the ultimate tensile strength (UTS), 0.2% yield strength (YS) and elongation to failure (Ef) at 175 °C of ~148 MPa, ~102 MPa and ~28%, improved by ~14.7%, ~24.3% and ~53.8%, respectively, compared to those of ATZ731 alloy. This enhancement is primarily owing to the refined microstructures and the high thermal stability of Al4Mm at the elevated temperature in contrast with that of the Mg17Al12 phase. The fracture modes are also discussed.

A continuous net-like eutectic structure enhances the corrosion resistance of Mg alloys

Mg alloys degrade rather rapidly in a physiological environment, although they have good biocompatibility andfavorable mechanical properties. In this study, Ti was introduced into AZ61 alloy fabricated by selective laser melting,aiming to improve the corrosion resistance. Results indicated that Ti promoted the formation of Al-enriched eutectic α phaseand reduced the formation of β-Mg17Al12 phase. With Ti content reaching to 0.5 wt.%, the Al-enriched eutectic α phaseconstructed a continuous net-like structure along the grain boundaries, which could act as a barrier to prevent the Mg matrixfrom corrosion progression. On the other hand, the Al-enriched eutectic α phase was less cathodic than β-Mg17Al12 phase inAZ61, thus alleviating the corrosion progress due to the decreased potential difference. As a consequence, the degradationrate dramatically decreased from 0.74 to 0.24 mg·cm-2·d-1. Meanwhile, the compressive strength and microhardness wereincreased by 59.4% and 15.6%, respectively. Moreover, the Ti-contained AZ61 alloy exhibited improved cytocompatibility.It was suggested that Ti-contained AZ61 alloy was a promising material for bone implants application.