High strength Mg-Zn-Y alloys reinforced synergistically by Mg₁₂ZnY phase and Mg₃Zn₃Y₂particle

Eight Mg_100-x-yZn_xY_y(at.%, x = 2–7.2, y = 4–7) alloys with atomic ratios of Y/Zn = 0.75–2 were designed and prepared by rapidly solidified powder metallurgy technology. The atomized powders with the Y/Zn atomic ratios larger than 1 contain α-Mg dendrite and network-like X-Mg₁₂ZnY compound, but those with the Y/Zn atomic ratios of 1 and 0.75 have W-Mg₃Zn₃Y₂particle besides the above two phases. After hot extrusion, network-like Mg₁₂ZnY phase was changed into acicular and plate-like shape. These as-extruded alloys exhibit excellent mechanical properties at room and elevated temperature. Especially, the ultimate tensile strength of as-extruded Mg₈₆Zn₇Y₇alloy reaches up to 541 MPa at room temperature and 297 MPa at 250 °C. HRTEM study reveals that Mg₁₂ZnY phase is composed of 18R LPSO structures. These sub-micrometer Mg₃Zn₃Y₂particles bring about dispersion strengthening to Mg₁₂ZnY phases, resulting in a synergistic strengthening of Mg₁₂ZnY phase and Mg₃Zn₃Y₂particle in the alloy which has the Y/Zn atomic ratio equal to or larger than 1. Therefore, the excellent mechanical properties of Mg₈₆Zn₇Y₇alloy are attributed to the second phase strengthening of LPSO phase and synergistic strengthening of Mg₁₂ZnY phase and Mg₃Zn₃Y₂particle.