Abstract: Low strength and poor corrosion resistance are two long-standing bottlenecks with dilute Mg alloys. Here, we report that the corrosion resistance of Mg-0.6Al-0.5Mn-0.2Ca (wt.%) alloy sheet can be significantly improved by micro-alloying with 0.3 wt.% Ce, and the strength can be considerably augmented after aging treatment. Simultaneous optimization of strength, ductility, and corrosion resistance is difficult due to the inherent trade-off in Mg alloys. Surprisingly, our aged Mg-0.6Al-0.5Mn-0.2Ca-0.3Ce alloy features with yield strength (YS) of ∼194 MPa, ultimate tensile strength (UTS) of ∼265 MPa, elongation to failure (EF) of ∼17.2%, and corrosion rate (CR) of 2.2 mm y^-1, the combination of which exhibits competitive advantage over other comparative dilute Mg alloys. It is found that Ce addition decreases the activity of cathodic phases, inhibits detrimental effects of Fe impurities, and forms a protective Ce-containing surface film. The high strength stems from the precipitation of ordered Guinier-Preston (G.P.) zones dispersed in uniform fine grains with an average grain size of ∼8.2 μm. The atomic-scale G.P. zones result in a noticeable age hardening response but do not act as crack initiation and propagation site, so our alloy also performs satisfactory ductility. This work sheds light on the design and fabrication of strong, ductile, and corrosion-resistant dilute magnesium alloys to be used in electronic products and automotive bodies.

Key words: Magnesium alloy, Micro-alloying, Aging, G.P. zones, Mechanical property, Corrosion