Enhanced mechanical and flame-retardant properties of as-extruded Mg-6Zn-1Mn magnesium alloy through Er and Ca addition

This study presents the development of two novel wrought nonflammable magnesium alloys based on the Mg-6Zn-1Mn (ZM61) system, which exhibit an exceptional combination of mechanical and flame-retardant properties. The effect of the single addition of 2.5 wt.% Er and co-addition of 2.0 wt.% Er and 0.5 wt.% Ca on the microstructure evolution, mechanical properties, and flame-retardant behavior of ZM61 alloy is systematically investigated. Results reveal that the addition of Er and Er&Ca promotes recrystallization, leading to refined grains and weakened basal texture. Notably, the co-addition of Er&Ca exhibits a more significant grain refinement effect. Microstructure analysis shows that the co-addition of Er&Ca alters the second-phase distribution, with the formation of Er-rich phases and Ca-containing compounds. The ZM61-0.5Ca-2.0Er alloy demonstrates excellent comprehensive properties, with an ultimate tensile strength of 360 MPa, a yield strength of 318 MPa, and an elongation of 13.7%. Notably, it achieves an ignition point exceeding 1000 ℃, attributed to the synergistic effect of Er&Ca, which forms a continuous and dense composite oxide layer consisting of Er₂O₃-CaO-MgO. These findings indicates that, compared with single addition of Er, the co-addition of Er&Ca is more efficient to enhance the multifunctionality of magnesium alloys for advanced applications requiring both good mechanical properties and excellent flame-retardant properties.