Effect of LPSO Phase-Stimulated Texture Evolution on Creep Resistance of Extruded Mg–Zn–Gd Alloys

The creep behavior and microstructures of extruded Mg97Zn1Gd2 alloys with long period stacking ordered (LPSO) phase have been investigated. Creep properties of extruded alloys depend on pre-extrusion aging temperature; the optimum aging temperature to obtain excellent creep resistance is between 623 and 723 K. In this temperature range, a multimodal microstructure develops during subsequent extrusion at 623 K. The α-Mg matrix are bimodally grained; that is, it consists of fine DRXed grains and <101̄0>//ED fiber-textured coarse grains. The LPSO phase grains also develop the <101̄0>//ED fiber texture. Coarse block-shaped LPSO phase promotes dynamic recrystallization in α-Mg matrix via particle stimulated nucleation, while both fine plate-shaped LPSO phase and solute-segregated stacking faults (SFs) stimulate <101̄0>//ED fiber texture evolution in the α-Mg matrix. The creep strength increases with increasing area fraction of the <101̄0>//ED fiber textured region (coarse α-Mg grains and LPSO phase grains). Formation of plate-shaped LPSO phase and/or solute-segregated SFs before extrusion is most desirable for enhancing the creep properties of extruded Mg97Zn1Gd2 alloys, due to LPSO phase-stimulated texture evolution.