Samarium and Yttrium co-doped synergistically improve corrosion resistance and mechanical properties of AZ61 alloy

The microstructure, corrosion resistance and mechanical properties of AZ61-0.5Y-xSm (x = 0, 1, 2, 3, 4, 5 wt%) alloy were systematically investigated with the addition of Samarium (Sm) and Yttrium (Y) as alloying elements. The results indicate that as the Sm content increases, the β-Mg 17 Al 12 phase gradually decreases, while the Al 2 Sm phase and Al 11 Sm 3 phase gradually increase, accompanied by a progressive refinement of the average grain size (AGS). The AZ61-0.5Y-3Sm alloy exhibited the optimal comprehensive performance in mass loss testing, electrochemical measurements, and tensile properties testing. Compared with AZ61-0.5Y, its average corrosion rate ( CR W ) decreases by approximately 46.88 %, while the ultimate tensile strength (UTS), yield strength (YS), and elongation (EL) increase by about 38.16 %, 33.61 %, and 47.86 %, respectively. The enhancement in corrosion resistance is primarily attributed to the addition of an appropriate amount of Sm, which reduces the micro-galvanic corrosion within the alloy and promotes electrochemical homogeneity of the matrix. Furthermore, the Al–Sm phase facilitates the formation of a continuous and stable Sm 2 O 3 protective film on the alloy surface, acting as an effective physical barrier. The improvement in mechanical properties results from the combined effects of grain refinement strengthening, solid solution strengthening, and second-phase strengthening.