Effect of pre-solution treatment on mechanical properties of as-extruded Mg96.9Zn0.43Gd2.48Zr0.15 alloy

The effect of pre-solution (T4) treatment on microstructure and mechanical properties of the as-extruded Mg96.9Zn0.43Gd2.48Zr0.15 alloy was investigated. The results suggested that the long period stacking ordered (LPSO) structure with a lamellar-shape morphology transformed from the decomposition of the primary Mg3Gd-type phase after the pre-solution (T4) treatment at 773 K for 12 h, and then grown into the block-shape LPSO structure until 120 h. The kinking band deformation occurred in the lamellar-shape and the block-shape LPSO structure during hot extrusion (HE). The morphologies and their kinking band of the LPSO structures influenced mechanical properties of the as-extruded alloys greatly. The best mechanical properties were found in the alloy B (T4 for 12 h+HE), which was ascribed to the lamellar-shape LPSO structure and its kinking deformation. Nevertheless, the mechanical properties of the alloy (T4 for 70 h+HE and 120 h+HE) decreased because of the fracture of the block-shape LPSO structure.