High strength Mg₉₄Zn_2.4Y_3.6 alloy with long period stacking ordered structure prepared by near-rapid solidification technology

To obtain high strength for near-rapid solidification (NRS) magnesium alloys, the microstructures and mechanical properties of the Mg₉₄Zn_2.4Y_3.6 (at%) alloys, which were prepared by ordinary and injection copper mold casting (ICMC), respectively, were investigated comprehensively. It has been shown that the microstructure of ICMC Mg₉₄Zn_2.4Y_3.6 alloy possesses the far-away-from equilibrium feature of NRS materials, which is composed of refined α-Mg grains with supersaturated Y and Zn, fine network-like long-period stacking-order (LPSO) phases and a few of Mg₂₄Y₅ particles. The interface between LPSO phase and α-Mg matrix is semi-coherent with the orientation relationship of [0002]_α//[112¯0]_LPSO, (101¯0)_α//(0002_)LPSO. The ICMC alloy exhibits enhanced mechanical properties with the ultimate tensile strength and elongation up to 355 MPa and 7% at room temperature, respectively, and with the ultimate tensile strength of 302 MPa at 150 °C. It can be concluded that the strengthening mechanisms of this ICMC alloy are attributed to the grain refinement, the solid solution effect, the secondary phase strengthening and the crystalline boundaries strengthening.