Corrosion of hot extrusion AZ91 magnesium alloy. Part II: Effect of rare earth element neodymium (Nd) on the corrosion behavior of extruded alloy

The corrosion behavior of extruded Nd-free AZ91 and extruded AZ91 + 1.5Nd alloy was investigated by weight loss and electrochemical measurements. The results showed that the extruded AZ91 + 1.5Nd alloy had higher corrosion resistance compared to the extruded Nd-free AZ91 alloy, which could been explained from point of view of microstructure changes: (1) the significant decrease of twins and dislocation decreased the anodic dissolution rate; (2) the micro-galvanic corrosion was inhibited by the formation of Al3Nd phase; and (3) Nd not only increased the percent of Non-Faraday process, but also led to anisotropic feature on the corrosion mechanism.

► Effect of Nd on the microstructure of extruded Mg alloy is studied by SEM/TEM.
► Role of Al3Nd on the micro-galvanic corrosion has been discussed in detail.
► Nd increases the Non-Faraday percent during the corrosion process.
► Nd has anisotropic influence on the corrosion mechanism.