Texture, microstructure and mechanical properties of an extruded Mg-10Gd-1Zn-0.4Zr alloy: Role of microstructure prior to extrusion

Abstract

The homogenized Mg-10Gd-1Zn-0.4Zr (wt.%) alloys with and without the LPSO phases were hot extruded, and then the texture evolution, microstructure and mechanical properties of the extruded alloys were investigated. The initial microstructure (prior to extrusion) containing no LPSO phases or only bulk/lamellar LPSO phases leads to a fully dynamically recrystallized (DRXed) grains, while that containing both the bulk and lamellar LPSO phases results in a bimodal structure with the coarse deformed grains and fine DRXed grains, indicating that the bulk LPSO phases can promote the DRX behavior via particle stimulated nucleation mechanism while the lamellar LPSO phases hamper the DRX behavior. An abnormal texture with <0001> parallel to the extrusion direction is observed in extruded alloys with a large average grain size, while a relatively weak basal texture is observed in small grains. The formation mechanism of this abnormal texture is due to the growth advantage of the DRXed grains with <0001> parallel to the extrusion direction over other grains. The contribution of each strengthening mechanism to the yield strength in four extruded alloys was calculated quantitatively, and the results show that grain refinement and solid solution strengthening mechanisms contribute the most to the yield strength in all extruded alloys. The contributions of dislocation strengthening and the secondary phase strengthening are enhanced in extruded alloys containing bulk LPSO phases, while that of texture strengthening is reduced. This work sheds light on controlling the mechanical properties of the extruded Mg alloys via the LPSO phases and texture.