Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《中国腐蚀与防护学报》
Abstract： The microstructure and corrosion morphology of extruded alloys Mg-xZn-yGd (x=1~3, y=0~3) were observed by optical microscopy (OM), scanning electron microscopy (SEM). Results show that after extrusion the microstructure of the alloys is obviously refined and further refined by Gd addition, i.e. the average grain size decreases from (30±3) μm for Mg-3Zn to (10±2) μm for Mg-3Zn-3Gd. The dynamic recrystallization occurs during the extrusion, while the second phase particles tend to distribute as belts along the extrusion direction. Mg-xZn-yGd alloy is sensitive to pitting corrosion in the Hank's solution. Among others the corrosion of Mg-3Zn-2Gd is the fastest, while that of Mg-3Zn is the slowest. After solid solution treatment, the corrosion rate of Mg-3Zn-2Gd and Mg-3Zn-3Gd decreases from (0.605±0.025) and (0.352±0.021) mg/(cm2·h) to (0.085±0.010) and (0.167±0.020) mg/(cm2·h) respectively. With increasing Zn content the corrosion current density decreases and the high-frequency capacitance increases gradually; with the increase of Gd content, the corrosion current density and high-frequency capacitance of the alloys rise firstly and then reduce gradually. Mg-3Zn alloy exhibits aminimum corrosion current density (8.65×10-3 mA/cm2)and a maximum Faraday resistance Rt (3312 Ω).
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《材料研究学报》
Abstract： Microstructure of hot rolled and annealed Mg-3Zn-2Gd alloy was characterized by optical microscopy and scanning electron microscopy. Meanwhile, their tensile mechanical properties at ambient temperature were tested. The results show that the microstructure of the alloy sheet is refined after rolling by the strain range from 23% to 67% and the average grain size decreases from 10 μm to 4 μm by the rolling strain of 67%. Lots of twins and shear bands in the initial microstructure decrease gradually. When the rolling strain increases to 67%, the shear bands disappear, and meanwhile the dynamic recrystalliza-tion grains and few twins exist, while the tensile mechanical properties of the alloy are enhanced significantly. Tensile strength σb and yield strength σ0.2 increase from 255 MPa and 215 MPa for the non-rolled alloy to 305 MPa and 300 MPa for the rolled alloy by strain 67% respectively, while the elongation δ first increases, and then decreases. After annealed at 573 K for 1 h, the rolled alloy experienced static recrystallization, in the meanwhile, the non-uniform deformation areas disappeared and finally showed a microstructure of fine and uniform equiaxed grains, and the relevant σb and σ0.2 decreased to 265 MPa and 235 MPa, respectively, while δ slightly increases to 19.0%. The tensile fracture consists of a large number of dimples presenting the typical characteristic of ductile fracture.
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