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Abstract: The microstructures and mechanical properties of Mg–5.3Zn–0.2Ca–0.5Ce (wt%) alloy fabricated by semi-continuous casting were investigated. The as-cast alloy consists of α-Mg, Ca2Mg6Zn3 and T′1 phase with orthorhombic structure (a=0.57nm, b=0.75nm and c=1.00nm). T′1 phase mainly distributes at the triple conjunctions while the Ca2Mg6Zn3 at the grain boundaries. The as-cast alloy exhibits high strength retention due to the stable Ca2Mg6Zn3 and T′1 phase at the grain boundaries. [Copyright &y& Elsevier]

Abstract: A large Mg-4.50Zn-1.13Ca (wt%) alloy ingot 350mm in diameter and 1730mm long was successfully fabricated by semi-continuous casting. The microstructures and mechanical properties of the as-cast and as-extruded alloys were investigated. The as-cast alloy exhibits uniform chemical composition and microstructure from the centre to the surface of the ingot and mainly consists of α-Mg and Ca2Mg6Zn3. The coarse grains and network-like second phases that are distributed at the grain boundaries result in poor mechanical properties for the as-cast alloy. The mechanical properties of the as-extruded alloys are significantly enhanced. The high yield strengths of the as-extruded alloys mainly result from the fine DRXed grain and the stronger basal texture. [Copyright &y& Elsevier]

Abstract: Extruded Mg–8.2Gd–3.8Y–1Zn–0.4Zr (wt%) alloy was subjected to ageing treatment at 200°C. The microstructures, textures and mechanical properties of the as-extruded and peak-aged alloys were investigated. Recrystallization occurred during ageing treatment. A large number of β′ phases were observed in the peak-aged alloy, accompanied with the decrease of the volume fraction of LPSO phases. A basal fiber texture and an unusual texture component with basal planes perpendicular to the extrusion direction were found in the as-extruded alloy, and the basal fiber texture was strengthened after ageing treatment. The peak-aged alloy exhibited a tensile yield strength (TYS), an ultimate tensile strength (UTS) and an elongation to failure of 395MPa, 470MPa and 8%, respectively, at ambient temperature, and 271MPa, 311MPa and 19%, respectively, at 300°C. The superior strength of the peak-aged alloy was mainly attributed to the precipitation of fine β′ phases, the remaining LPSO phases and the texture modification. [Copyright &y& Elsevier]

Abstract: The microstructure and mechanical properties of Mg–8.2Gd–3.8Y–1.0Zn–0.4Zr (wt%) alloy sheets produced by combined processes of extrusion, large-strain hot rolling and ageing treatment were investigated. The sheet rolled at 300°C was mainly composed of deformed grains while that rolled at 400°C was fully recrystallized, and the LPSO phase distributed at the grain boundaries in both sheets. The sheet rolled at 300°C and then peak-aged at 200°C exhibits 0.2% proof stress (PS) of 454MPa, ultimate tensile strength (UTS) of 469MPa and elongation to failure of 1.3% at ambient temperature, and 0.2% PS of 413MPa, UTS of 457MPa and elongation to failure of 6.8% at 200°C, respectively. While the sheet rolled at 400°C and peak aged at 200°C had lower 0.2% PS and superior ductility. The improvement of strength is ascribed to the fine β′ phase precipitated within the grains, the LPSO phase and dispersed cuboid Mg–Gd–Y containing phase located at the grain boundaries. [Copyright &y& Elsevier]

Abstract: The extruded Mg–8.2Gd–3.8Y–1.0Zn–0.4Zr (wt%) alloy were subjected to large-strain hot rolling with different final rolling temperatures. The microstructural evolution and mechanical properties of the sheets were investigated. The microstructure became homogeneous after hot rolling process and long period stacking ordered (LPSO) phase distributed at grain boundaries along rolling direction. The sheet rolled at 300°C was composed of deformed grains, substructures and excessive dislocations. With increasing final rolling temperatures from 300°C to 400°C, the volume fraction of recrystallized grains with relatively random orientations increased significantly. The strength of the rolled sheets was improved while the ductility was deteriorated with decreasing final rolling temperatures. The tensile yield strength and ultimate tensile strength of the sheet rolled at 300°C reached 320MPa and 416MPa, respectively with the elongation to failure of 5.3%. The mechanical anisotropy of the rolling sheet became unity when rolled at higher temperature of 400°C due to the formation of weaker basal texture. [Copyright &y& Elsevier]

Abstract: Different cooling processes, such as quenching in warm water and cooling in furnace, were introduced to homogenize Mg–8.2Gd–3.8Y–1.0Zn–0.4Zr (wt%) alloy. Microstructure evolution and mechanical properties of the homogenized alloy were investigated. The as-quenched sample was comprised of α-Mg matrix, Mg5RE phase and 18R LPSO phase distributed at the grain boundaries and a few of RE-rich particles distributed randomly. During the process of cooling in furnace, Mg5RE and 18R LPSO phases were transformed into block-shaped 14H LPSO phase and lamellar-shaped 14H LPSO phase, respectively, due to the diffusion of solute atoms into the α-Mg matrix. Furthermore, the lamellar-shaped 14H LPSO phase grew and ran through the whole grains. The as-quenched sample exhibits tensile yield strength of 130MPa, ultimate tensile strength of 206MPa and elongation to failure of 5.5%, while the sample cooled in the furnace exhibits higher tensile yield strength but lower ultimate tensile strength and ductility due to the coarse grains and formation of block-shaped 14H LPSO phase. [Copyright &y& Elsevier]

Abstract: The Mg–8.2Gd–3.8Y–1.0Zn–0.4Zr (wt.%) alloy was hot rolled with different final rolling reductions at 400°C. The microstructure evolution and texture of the sheets were analyzed, and their effect on the mechanical properties was discussed. All of the rolled sheets consist of fine dynamically recrystallized grains with almost random orientation, large deformed grains with strong basal texture. In addition, bent lamellar-shaped long period stacking ordered (LPSO) phases due to kink deformation were observed in the deformed grains. The volume fraction of the dynamic recrystallization increased with increasing final rolling reduction and the basal texture weakened gradually. The strength of the alloy sheets changed a little with increasing final rolling reduction, while the yield anisotropy and the ductility were significantly improved. The sheet final-rolled with thickness reduction of 60% exhibits tensile yield strength of 306MPa, ultimate tensile strength of 393MPa and elongation to failure of 14.6% at ambient temperature, and tensile yield strength of 264MPa, ultimate tensile strength of 345MPa and elongation to failure of 19.4% at 250°C. [Copyright &y& Elsevier]

Abstract: Mg-8.2Gd-3.8Y-1.0Zn-0.4Zr alloy ingot with diameter of 280mm and length of 2940mm was successfully fabricated by semi-continuous casting. The microstructure and mechanical properties of the large ingot at different locations were investigated. The concentration of the RE and Zn elements distributed almost homogeneously through the whole alloy ingot. The average grain size decreased from the center to the surface of the alloy ingot, while the strength and ductility were improved gradually. The main eutectic compounds located at the grain boundaries were (Mg,Zn)3(Gd,Y) phase, adjacent to these eutectic compounds the 14H-type long period stacking ordered (LPSO) phase formed. Furthermore, some block-shaped Mg24(Gd,Y)5 phase and isolated Zr cores can be recognized in the interior of the grains. [Copyright &y& Elsevier]

Abstract: In this research, the as-cast and as-homogenized Mg–8.2Gd–3.8Y–1.0Zn–0.4Zr alloy were subjected to the hot rolling with the same processing parameters. The microstructure and mechanical properties of the two kinds of as-rolled sheets were investigated. The sheet rolled from the as-cast alloy was mainly composed of recrystallized α-Mg grains surrounded by Mg3(Gd,Y) eutectic compounds. While the sheet rolled from the as-homogenized alloy was composed of large deformed grains with long-period stacking ordered (LPSO) phase inside and fewer recrystallized α-Mg grains, and exhibited higher strength due to the deformed grains with stronger basal texture and larger volume fraction of long-period stacking ordered (LPSO) phase. [Copyright &y& Elsevier]

Abstract: Mg–8.2Gd–3.8Y–1.0Zn–0.4Zr alloy sheets containing long period stacking ordered (LPSO) phase were prepared by hot rolling at 400°C with total reduction of 96%. Microstructure evolution of the sheets during hot rolling was investigated, and its influence on mechanical properties was discussed. Twinning occurred during the early stage of hot rolling, and disappeared after total reduction higher than 89%. Average grain size was gradually refined, microstructure became much more homogeneous and volume fraction of LPSO phase decreased with increasing rolling reduction. Furthermore, the type of LPSO phases far from and near the block shaped phases were identified to be different. Basal texture was obtained during rolling process, but the intensity declined with the further rolling, which is mainly due to the dynamic recrystallization and the addition of RE elements. The as-rolled sheet with 96% reduction shows excellent mechanical properties: yield strength of 318MPa, ultimate tensile strength of 403MPa and elongation to failure of 13.7% at ambient temperature along the rolling direction. [Copyright &y& Elsevier]

Abstract: In this study, firstly, dynamic microstructural changes of an as-cast Mg–5.0 Zn–0.9 Y–0.16 Zr (wt.%) alloy (designated ZWK510) during hot extrusion at 350°C and a ram speed of 3.33mms−1 was systematically investigated by electron backscattering diffraction (EBSD) analysis. The dynamic recrystallization (DRX) mechanism during hot extrusion was discussed. Then, the effect of microstructure and texture on the mechanical properties of the as-extruded alloy specimens at room temperature was discussed. The as-cast ZWK510 alloy consists of a-Mg and quasicrystalline I-phase. During hot extrusion at 350°C, the main DRX mechanism is the continuous DRX near the original grain boundaries. The I-phase can accelerate the DRX behavior near these areas by obstructing the slip of dislocations. The deformation twins and massive blocky substructures formed in original grains can coordinate the DRX process near the original grain boundaries, however the DRX seldom occurs inside of these area. After further deformation, these deformation twins and massive blocky substructures are elongated along the material flow and become so-called unDRXed area, then a bimodal “necklace structure” composed of fine DRXed grains of about 2.1μm and unrecrystallized coarse area is formed. The extruded ZWK510 alloy shows a DRX ratio of about 58% and a typical basal fiber texture of extrusion direction (ED). In the DRXed area around the crushed eutectic I-phase a large number of fine I-phase precipitates are observed pinning at the newly formed DRXed grain boundaries. The 0.2% proof strength and the ultimate tensile strength of the extruded ZWK510 alloy specimen are 317 and 363MPa, respectively, with an elongation to failure of 12%, which have been attributed to strong basal fiber texture, refined grain size as well as the existence of fine precipitates formed during the hot extrusion. [Copyright &y& Elsevier]

Abstract: The effect of trace Mn addition on the microstructure, texture and mechanical properties of the as-cast and as-extruded Mg–5.25wt.% Zn–0.6wt.% Ca (ZX51) alloys was investigated in this study. Mn addition had a negligible effect on the grain size of the as-cast ZX51 alloy. However, the addition of Mn led to the obvious decrease of grain size in the as-extruded Mg–5.25wt.% Zn–0.6wt.% Ca–0.3wt.% Mn (ZXM510) alloy, because the Mn addition restricted the grain growth during the hot extrusion process. After the addition of Mn, the basal fiber texture with most of {0002} planes parallel to the extrusion direction (ED) was significantly enhanced in the as-extruded ZXM510 alloy. Both tensile yield strength (TYS) and ultimate tensile strength (UTS) were increased in the as-extruded ZXM510 alloy, while the ductility was slightly decreased, which was ascribed to the grain refinement and texture strengthening. [Copyright &y& Elsevier]