Abstract: Simultaneously improving the mechanical properties and corrosion resistance of magnesium (Mg) alloys is a long-standing challenge to be solved in their engineering applications. In this work, we find that trace Er addition can improve the mechanical and anti-corrosion properties of Mg-1.4Al-0.4Mn-0.4Ca-0.3Er (wt%, AMXE) dilute alloy synergistically, especially reducing the corrosion rate (0.75 mm y^-1) by one order of magnitude compared with the reference Mg-1.4Al-0.4Mn-0.4Ca (AMX) alloy and making it comparable to that of high-purity Mg. Adding trace Er reduces the dynamic recrystallization degree and increases the strengthening phase particles, which is mainly responsible for the increase of yield strength by 42 MPa. The addition of Er promotes the formation of much less noble Al₈Mn₄Er with effective Fe trapping ability and induces dislocation segregation, thus dramatically reducing micro-galvanic corrosion tendency. Meanwhile, Er addition promotes the formation of a more passivation and dense corrosion film. These two factors together lead to the extremely low corrosion rate of AMXE alloy. Our findings are expected to promote the development of low alloyed high performance Mg alloys.

Key words: Magnesium alloy, Mechanics-corrosion synergy, Rare earth element, SKPFM