Effects of Mn addition and X-phase on the microstructure and mechanical properties of high-strength Mg–Zn–Y–Mn alloys

The effects of Mn addition and the volume fraction of X-phase on the microstructure and mechanical properties of the Mg–Zn–Y–Mn alloys with a Zn/Y ratio (at%) of approximately 0.5 have been systematically investigated. The results show that the addition of Mn produces fine Mn particles dispersed in the matrix, which improve the mechanical properties of the as-extruded Mg–Zn–Y alloy significantly through refining the grain size. XRD analysis reveals that the phases of the Mg–Zn–Y–Mn alloys consist mainly of α-Mg, X-phase and Mn. In addition, tensile test results show that the mechanical properties of the as-extruded Mg–Zn–Y–Mn alloys depend closely on the volume fraction of the X-phase. When the Zn/Y ratio is constant, the as-extruded Mg95.21Zn1.44Y2.86Mn0.49 alloy has the best mechanical properties, exhibiting a tensile strength of 421 MPa, a yield strength of 333 MPa and an elongation of 5.85%. The high strength is mainly due to the strengthening by the refinement of α-Mg matrix grains through increase in amount of X-phase.