Effect of Gd/Nd ratio on mechanical and biocorrosion properties of as-extruded Mg-Nd-Gd-Sr-Zn-Zr alloys

Mg-(4-x) Nd-x Gd-0.3Sr-0.2Zn-0.4Zr (wt.-%, x=0, 1, 2, and 3) alloys with various Gd/Nd ratios were prepared by gravity casting, solution-treated and then hot extruded. The microstructures, mechanical properties at room temperature, corrosion behaviour in simulated body fluid of the as-extruded alloys were studied. The as-extruded alloys undergo partially dynamic recrystallisation, and the equiaxed grains become coarse with increasing Gd/Nd ratio. The strength of the alloys increases first and then decreases with increasing the Gd/Nd ratio; however, the elongation of the alloys increases apparently with increasing Gd/Nd ratio. Both immersion test and polarisation test indicate that the corrosion rate of the as-extruded alloys is reduced with increasing the Gd/Nd ratio, and the alloys exhibit relatively uniform corrosion morphologies.