Improved SCC resistance of biodegradable Mg–Zn–Zr alloy by rare-earth element addition

SCC characteristics of the ternary Mg–3Zn–0.5Zr (ZK30) and quaternary Mg–3Zn–0.5RE–0.5Zr (ZEK300) alloys were investigated using the slow strain rate shear (SSRS) test, and compared to that of commercially pure (CP) Mg. When tested in the simulated body fluid (SBF), ductility and the ultimate shear stress (USS) of all materials decreased due to the adverse effects of the corrosive medium. The quaternary alloy showed the lowest USS drop during testing in the SBF solution and the highest SCC resistances. The observed improvement in the SCC resistance of the ZEK300 alloy was ascribed to the presence of a more protective corrosion layer on its surface, facilitated by its fine-grained structure as well as the presence of fine CeZn 5 second phase particles.