Effects of low-level Er on the microstructure, mechanical and anti-corrosion properties of Mg-1Zn-0.3Zr alloy

To enhance the mechanical properties and corrosion resistance of biodegradable Mg alloys, varying amounts of Er (0, 0.5, 1, 1.5, 2, and 3 wt%) are added to the Mg-1Zn-0.3Zr alloy in this study. The phases of Mg 3 Er 2 Zn 3 and MgEr are observed after Er doping. As the Er content increases, there is a progressive reduction in grain size, accompanied by a gradual increase in the volume fraction of second phases. The mechanical properties and corrosion resistance initially improve, followed by a gradual decline as the Er content continues to rise. The alloy with 1.5 wt% Er exhibits superior overall performance. Compared with the Mg-1Zn-0.3Zr alloy, the yield strength, ultimate tensile strength, and elongation increase by 18.3%, 34.3%, and 42%, respectively, while the corrosion rate decreases by 36.4%. The enhancement in mechanical properties is attributed to grain refinement and the strengthening of second phases. The improvement in corrosion resistance is linked to the formation of Er 2 O 3 , an elevated potential, and a lower potential difference between the second phases and Mg matrix. Furthermore, it is confirmed that Ca and P ions are enriched in the outer layer of corrosion products. • Er addition results in a progressive reduction in grain size, from 153 μm to 87 μm. • Addition of 1.5% Er elevates the alloy potential and reduces the potential difference between Mg matrix and second phases. • ZK-1.5Er alloy demonstrates the superior mechanical properties and bio-corrosion resistance. • Ca and P concentrate in the outer layer of corrosion product for the alloys in SBF. • Formation of Er 2 O 3 results in a passivation and dense corrosion film.