Effects of Sc on microstructure, mechanical properties and corrosion behavior of Mg-0.5Zn-0.5Nd-xSc alloys

Sc-containing Mg alloys have attracted increasing attention since Sc is believed to improve the mechanical properties and corrosion resistance of the alloys. In this work, effects of Sc on the microstructure, mechanical properties and corrosion behavior of Mg-0.5Zn-0.5Nd-xSc were investigated. The results indicated the moderate refinement effect of Sc element in the as-cast alloys, which improves their mechanical properties. However, the uneven distribution of Sc element was found in the as-cast alloys. The segregation of Sc element was not ameliorated after homogenization and hot extrusion, resulting in the formation of curly Sc-poor/Sc-rich bands (on the surface perpendicular to ED) and vertical Sc-poor/Sc-rich bands (on the surface parallel to ED) in the extruded alloys. The relevant results found that the addition of Sc elements affected the corrosion resistance of the alloys in two conflicting ways. In specific, the formed Sc2O3 in the corrosion products layer enhanced the corrosion resistance of the alloys, while, the Sc segregation in the alloys and the precipitation of metallic Sc in the corrosion products promoted the galvanic corrosion of the alloys.