Influence of the morphology of long-period stacking ordered phase on the mechanical properties of as-extruded Mg–5Zn–5Y–0.6Zr magnesium alloy

In this study, the influence of the different microstructure and morphology of long-period stacking ordered (LPSO) X-phase (Mg12YZn) on the mechanical properties of as-extruded Mg–5Zn–5Y–0.6Zr (wt.%, nominal chemical composition) alloys, tailored by different extrusion parameters, were investigated using tensile tests, optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectrometer, X-ray diffractometer and transmission electron microscopy. Under an extrusion ratio of 11 and extrusion temperature set at 450°C, the discontinuous network morphology of LPSO phases along the grain boundaries created an alloy that had good ductility, characterised by 20.3% elongation. Under an extrusion ratio of 89 and extrusion temperature set at 500°C, the dispersive block-shaped LPSO phases and refined grains made the alloy to obtain an ultimate tensile strength of 412MPa, tensile yield strengths of 380MPa and elongation of 11.8%. Therefore, while the existence of LPSO phases contributes to the alloy strengthening, the morphology regulation and control of LPSO phases can further enhance their strength.