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 degrees 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 degrees C, the dispersive block-shaped LPSO phases and refined grains made the alloy to obtain an ultimate tensile strength of 412 MPa, tensile yield strengths of 380 MPa 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. (c) 2012 Elsevier B.V. All rights reserved.