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

Abstract

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 <10\bar{1}0>//ED fiber-textured coarse grains. The LPSO phase grains also develop the <10\bar{1}0>//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 <10\bar{1}0>//ED fiber texture evolution in the α-Mg matrix. The creep strength increases with increasing area fraction of the <10\bar{1}0>//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.