Extruded Microstructures and Corrosion Properties of Biomedical Mg-6Zn-xGd Alloys

Extruded microstructures of Mg-6Zn-xGd (x=0 similar to 4) alloys were investigated by optical microscopy (OM) and scanning electron microscopy (SEM). The tensile mechanical property and corrosion property were also tested. The results show that the extruded microstructure is refined obviously with increasing the Gd content, and the average grain size decreases from 12 mu m for Mg-6Zn alloy to 2 gm for Mg-6Zn-3.41Gd alloy. Extruded tensile mechanical property is enhanced significantly. Tensile strength sigma(b) and yield strength sigma(0.2) increase gradually from 295 MPa and 193 MPa for Mg-6Zn alloy to 350 MPa and 325 MPa for Mg-6Zn-3.41Gd alloy, respectively. Elongation 6 first decreases, and then increases, which is not lower than 10%. Extruded Mg-6Zn alloy exhibits a slow corrosion rate with typical local corrosion. When a little Gd (0.66 wt%) is added, the corrosion rate increases slightly; but its corrosion becomes more uniform, changing to the uniform corrosion. When more Gd (1.66 wt% and 3.41 wt%) is added, the corrosion resistance deteriorates sharply.