ISSN 0412-1961
CN 21-1139/TG
Started in 1956

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Magnesium rare-earth (Mg-RE) alloy castings with a large size and complex structure exhibit versatile prospects in critical aircraft, aerospace, and defense fields owing to their ultralow density, excellent specific strength, and high-temperature resistance. The grain refinement of cast Mg-RE alloys. . .
 Acta Metall Sin, 2022 Vol. 58 (4): 385-399    DOI: 10.11900/0412.1961.2021.00519
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 Present Status For Rolling TiAl Alloy Sheet PDF (3702KB)
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 11 May 2022, Volume 58 Issue 5 Previous Issue
 Select Corrosion and Cavitation Erosion Behavior of GLNN/Cu Composite in Simulated Seawater PAN Chengcheng, ZHANG Xiang, YANG Fan, XIA Dahai, HE Chunnian, HU Wenbin Acta Metall Sin. 2022, 58 (5): 599-609.   DOI: 10.11900/0412.1961.2021.00333 Abstract   HTML   PDF (3618KB) Herein, three-dimensional graphene-like nanosheet network (3D-GLNN)/copper (Cu) materials were synthesized using hop-pressing (HP) and hot-rolling (HR) methods and their corrosion resistance and mechanism were investigated using polarization curves, electrochemical impedance spectroscopy (EIS), and weight loss data after a cavitation corrosion test. Microstructural characterization results revealed that the 3D-GLNN structure was intact in the bulk composites, thereby restricting the effective grain growth of the Cu matrix. Compared with pure Cu, the Vickers hardness of 3D-GLNN/Cu fabricated using the HP and HR methods improved by 8% and 46%, respectively. Polarization curve results indicated that the anodic dissolution current of 3D-GLNN/Cu was considerably lower than that of pure Cu, indicating that 3D-GLNN/Cu exhibited better corrosion resistance. EIS measurements under a corrosion potential revealed that the electrode process kinetics was complex, with both charge and mass transfer controlling it. By extending the immersion time from 1 h to 9 d, the corrosion potential first became positive and then became negative. The capacitance arc at a high-frequency EIS range first increased and then decreased, attributed to the formation and detachment of a CuCl salt film. Diffusion impedance was observed in the low-frequency EIS range, with a phase angle of 18°-23°, indicating that the mass transfer process was not attributed to a single species but controlled by anodic and cathodic reactants. The constant phase angle element (CPE) behavior of the electrochemical system was further evaluated using the ohm-corrected phase angle and impedance modulus. The high-frequency phase angle was greater than -90 $°$, while the slope of impedance modulus was approximately -0.9; thus, the CPE was used to model the EIS data. The CPE behavior was attributed to the surface distribution of the charge transfer resistance and interface capacitance, implying a time-constant dispersion on the surface. Weight loss data after the cavitation corrosion test indicated that pure Cu showed better cavitation resistance than 3D-GLNN/Cu fabricated using the HR and HP methods. This is because of the difference in the elastic modulus between the graphene and Cu matrix that caused deformation dissonance during cavitation erosion.
 Select Detwinning Behaviors and Dynamic Mechanical Properties of Precompressed AZ31 Magnesium Alloy Subjected to High Strain Rates Impact CHEN Yang, MAO Pingli, LIU Zheng, WANG Zhi, CAO Gengsheng Acta Metall Sin. 2022, 58 (5): 660-672.   DOI: 10.11900/0412.1961.2021.00117 Abstract   HTML   PDF (4382KB) To investigate the detwinning behaviors and dynamic mechanical properties of a precompressed rolled AZ31 magnesium alloy sheet impacted under high strain rates, the as-received sheet was precompressed along the rolling direction (RD) to the true strain of 4% for inducing { $101¯2$} tensile twins. The as-received and precompressed rolled AZ31 magnesium alloy sheets were impacted along the normal direction (ND) using a split Hopkinson pressure bar experiment apparatus at strain rates of 700, 1000, 1300, and 1600 s-1. Microstructural characteristics of the as-received, precompressed, and impacted specimens were analyzed and compared by an electron backscatter diffraction technology. The results show that in the precompressed specimen, the density of the basal texture was weakened and a new twin texture with the c-axis paralled to RD was formed. The average grain size of the precompressed specimen decreased visibly as a result of the parent grains being subdivided by tensile twin boundaries. The dominant deformation mechanism of the precompressed rolled AZ31 magnesium alloy impacted along ND is detwinning. With increasing the strain rate, the initial basal texture recovered, the average grain size increased, and the average twin thickness decreased. Compared with the precompressed specimen, the as-received specimen impacted along ND exhibited higher strength and lower formability. The precompressed specimen demonstrated greater strain rate sensitivity during plastic deformation.
 Select Creep Behavior of FGH96 Superalloy at Different Service Conditions PENG Zichao, LIU Peiyuan, WANG Xuqing, LUO Xuejun, LIU Jian, ZOU Jinwen Acta Metall Sin. 2022, 58 (5): 673-682.   DOI: 10.11900/0412.1961.2021.00207 Abstract   HTML   PDF (4862KB) The FGH96 superalloy is extensively used as a gas turbine disk under high temperature due to its excellent tensile and creep properties. With recent developments in the aviation industry, the velocity of the aircraft has increased significantly, thereby increasing the temperature and stress on the turbine disk materials during their service. Therefore, creep deformation is crucial in the turbine disk superalloy. In this study, the creep characteristics of FGH96 superalloy were systematically studied at 650-750oC and 690-810 MPa and the creep mechanism of the alloy under different service conditions was investigated via SEM, EBSD, and TEM. For the creep temperature of 704oC, the creep properties of the alloy decreased with the increase in stress level. When the applied loading stress was 690 MPa, the creep properties of FGH96 alloy decreased significantly with the increase in temperature, and its steady-state creep strain rate was more sensitive to the service temperature. Further, every 30oC increase in the service temperature increased the creep rate by an order of magnitude. For the temperature in the range 650-750oC and the applied loading stress in the range 690-810 MPa, the creep deformation of the alloy was dominated by dislocation slip and resulted in various micro-twins on the continuous ($111¯$) planes. Moreover, the creep fracture of FGH96 alloy presented typical intergranular fracture under different service conditions in this study.