Microstructure development and biodegradation behavior of additively manufactured Mg-Zn-Gd alloy with LPSO structure

Biodegradable magnesium (Mg) alloy has been considered as a new generation of orthopedic implant ma-terial. Nevertheless, local corrosion usually occurs since the severe micro-galvanic behavior among alpha-Mg and precipitates, and results in too rapid degradation. In this study, porous Mg-Zn-Gd part was fabricated using laser additive manufacturing combined with solution heat treatment. During heat treatment, the precipitated beta-(Mg,Zn)(3)Gd phase dissolved in alpha-Mg, and reduced the energy threshold of stacking faults on basal planes, which finally triggered the formation of long period stacking ordered (LPSO) phase. The LPSO phases owned minor potential difference with alpha-Mg, thus causing less micro-galvanic corrosion ten-dency as compared to beta-(Mg,Zn)(3)Gd phase. More importantly, they were uniformly distributed within the alpha-Mg grains and showed different orientations between adjacent grains. As a result, the LPSO-reinforced Mg-Zn-Gd tended to expand laterally during corrosion evolution, and achieved uniform degradation with a considerably reduced degradation rate of 0.34 mm/year. Moreover, in-vitro cell tests further proved its favorable biocompatibility. This work highlighted the additively manufactured Mg-Zn-Gd with LPSO structure showed great potential for orthopedic application. (c) 2022 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Automated summary

In this study, porous Mg-Zn-Gd part was fabricated using laser additive manufacturing combined with solution heat treatment. The formation of long period stacking ordered (LPSO) phase reduced the micro-galvanic corrosion tendency and achieved uniform degradation with a considerably reduced degradation rate of 0.34 mm/year. In-vitro cell tests further proved its favorable biocompatibility. The additively manufactured Mg-Zn-Gd with LPSO structure showed great potential for orthopedic application.