Enhanced Mechanical Properties and Corrosion Resistance by Minor Gd Alloying with a Hot-Extruded Mg Alloy

The microstructure, mechanical properties, and corrosion resistance to simulated body fluid solution behavior of as-extruded Mg-1.8Zn-0.5Zr alloys with different Gd additions are investigated. It is found that dynamic recrystallization occurs in the alloys during extrusion and the grain size gradually decreases with Gd alloying. The mechanical properties and corrosion resistance to simulated body fluid of the investigated alloys enhance firstly and then weaken with the increase in Gd content. The results reveal that the Mg-1.8Zn-0.5Zr with a 1.5 wt.% Gd addition has optimized mechanical properties and corrosion resistance. A three-stage corrosion mechanism, including sequential stages from hydroxidation, phosphatization and hydroxidation, to formation-dissolution dynamic equilibrium, is proposed through electrochemical measurements and corroded surface analyses. This study reveals the extruded Mg-1.8Zn-0.5Zr-1.5Gd alloy can be regarded as a potential candidate for using as biodegradable magnesium implants.