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ISSN: 1006-7191
CN: 21-1361/TG
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  Current Issue
      10 November 2019, Volume 32 Issue 11 Previous Issue    Next Issue
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    Orginal Article
    Evolution of Microstructure, Residual Stress, and Tensile Properties of Mg-Zn-Y-La-Zr Magnesium Alloy Processed by Extrusion
    Huseyin Zengin, Yunus Turen, Muhammet Emre Turan, Fatih Ayd?n
    Acta Metallurgica Sinica(English letters), 2019, 32 (11): 1309-1319.  DOI: 10.1007/s40195-019-00901-7
    Abstract   HTML   PDF (5615KB) ( 45 )

    The microstructure, texture, residual stress, and tensile properties of Mg-6Zn-2Y-1La-0.5Zr (wt%) magnesium alloy were investigated before and after extrusion process, which performed at 300 °C and 400 °C. The microstructural characterizations indicated that the as-cast alloy was comprised of α-Mg, Mg-Zn, Mg-Zn-La, and Mg-Zn-Y phases. During homogenization at 400 °C for 24 h, most of the secondary phases exhibited partial dissolution. Extrusion process led to a remarkable grain refinement due to dynamic recrystallization (DRX). The degree of DRX and the DRXed grain size increased with increasing extrusion temperature. The homogenized alloy did not show a preferential crystallographic orientation, whereas the extruded alloys showed strong basal texture. The extrusion process led to a significant improvement on the compressive residual stress and mechanical properties. The alloy extruded at 300 °C exhibited the highest basal texture intensity, the compressive residual stress and hardness, and yield and tensile strengths among the studied alloys.

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    Dynamic Compressive Property of Closed-Cell Mg Alloy Composite Foams Reinforced with SiC Particles
    Wen-Zhan Huang, Hong-Jie Luo, Yong-Liang Mu, Jian-Rong Xu, Ai-Chun Zhao
    Acta Metallurgica Sinica(English letters), 2019, 32 (11): 1320-1328.  DOI: 10.1007/s40195-019-00908-0
    Abstract   HTML   PDF (2241KB) ( 26 )

    The high-strain-rate mechanical response of Mg alloy/SiCp composite foams has received increased attention in recent years due to their light weight and potential to absorb large amounts of energy during deformation. Dynamic compressive properties of closed-cell Mg alloy/SiCp composite foams with different relative densities (0.162, 0.227 and 0.351) and different SiCp additions (0, 4 and 8 wt%) have been investigated using Split-Hopkinson pressure bar. It is shown that peak stress and energy absorption capacity significantly increase as the relative density increases at the range of testing strain rates. Peak stress and energy absorption display strain rate dependence. The peak stress of specimens with 0 wt% and 4 wt% SiC particles additions grows with increasing strain rate. Meanwhile, the increment in the peak stress of specimens with 8 wt% addition is not significant with strain rate increasing. The increase in strain rate increases the energy absorption capacity. The suitable amount of SiC particles addition has great advantages over increasing the peak stress and energy absorption capacity at the high strain rate. The strain-rate-sensitive matrix, cell morphology, morphological defects and gas pressure have an impact on the strain-rate sensitivity of Mg alloy/SiCp composite foams.

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    Powder Size Influence on Tensile Properties and Porosity for PM Ti2AlNb Alloy Prepared by Hot Isostatic Pressing
    Zheng-Guan Lu, Jie Wu, Lei Xu, Rui Yang
    Acta Metallurgica Sinica(English letters), 2019, 32 (11): 1329-1336.  DOI: 10.1007/s40195-019-00928-w
    Abstract   HTML   PDF (2549KB) ( 19 )

    Pre-alloyed powder of Ti2AlNb alloy was prepared by electrode induction gas atomization method, and the powder was screened into five kinds of powder size distribution. Fully dense Ti2AlNb alloy was prepared by powder metallurgy (PM) using hot isostatic pressing. The properties of pre-alloyed powder and PM Ti2AlNb alloy were tested. Results show that mean grain size of PM Ti2AlNb alloy is influenced by powder particle size, but particle size has no significant influence on tensile properties. Finer Ti2AlNb powder has low Argon gas bubble ratio and high oxygen content, and poor flowability of finer powder increases the degree of difficulty during degassing. As a result, big pores (>?50 μm) are observed in PM Ti2AlNb alloy prepared by finer powder and cause plasticity loss of tensile properties. In order to get a better comprehensive properties of PM Ti2AlNb alloy, powder with an average size (~?100 μm) is suggested.

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    Effect of Ag on the Microstructure, Mechanical and Bio-corrosion Properties of Fe-30Mn Alloy
    Ruo-Yu Liu, Ran-Gan He, Yan-Xia Chen, Sheng-Feng Guo
    Acta Metallurgica Sinica(English letters), 2019, 32 (11): 1337-1345.  DOI: 10.1007/s40195-019-00911-5
    Abstract   HTML   PDF (3587KB) ( 29 )

    In the current work, biodegradable Fe-30Mn-XAg (X?=?1, 2, 5, 10 wt%) alloys were prepared by the rapid solidification with copper-mold-casting technology. Phase analysis demonstrates that Fe-30Mn-XAg alloys consist of austenite γ phase with a fcc structure and martensite ε phase with a hcp structure. The yield strength of the samples increases with increasing Ag contents. Compared with Fe-30Mn alloy, the degradation rates of Fe-30Mn-XAg in Hank’s solution are significantly improved. Cytotoxicity evaluation reveals that the Fe-30Mn-1Ag and Fe-30Mn-2Ag alloys perform less toxicity on the Human Umbilical Vein Endothelial Cells (HUVEC), while Fe-30Mn-5Ag and Fe-30Mn-10Ag alloys perform no toxicity on it. The contact angles of deionized water on the Fe-30Mn-XAg alloy surface were ranged from 55° to 69°, which is beneficial to the adhesion and growth of the cells. Besides, the addition of Ag leads to a much lower M/H slope, particularly for the Fe-30Mn-5Ag alloy exhibiting a non-magnetic property as SS316L. Therefore, the present Fe-30Mn-XAg alloys would be potential candidates for degradable metals.

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    Masing Behavior and Microstructural Change of Quenched and Tempered High-Strength Steel Under Low Cycle Fatigue
    Feng-Mei Bai, Hong-Wei Zhou, Xiang-Hua Liu, Meng Song, Ya-Xin Sun, Hai-Long Yi, Zhen-Yi Huang
    Acta Metallurgica Sinica(English letters), 2019, 32 (11): 1346-1354.  DOI: 10.1007/s40195-019-00893-4
    Abstract   HTML   PDF (2772KB) ( 18 )

    Low cycle fatigue behavior of a quenched and tempered high-strength steel (Q960E) was studied in the strain amplitude ranging from ± 0.5% to ± 1.2% at room temperature. As a result of fatigue loading, the dislocation structural evolution and fracture mechanism were examined and studied by transmission electron microscopy and scanning electron microscopy (SEM). The results showed that this Q960E steel showed cyclic softening at different strain amplitudes, and the softening tendency was more apparent at strain amplitude of ± (0.6-1.2)% than that at ± 0.5%. The reduction in dislocation density with increasing strain amplitude is responsible for the softening tendency of cyclic stress with the strain amplitude. The material illustrates near-Masing behavior at strain amplitude ranging from ± 0.6% to ± 1.2%. The near-Masing behavior of Q960E high-strength steel can be the result of stability of martensite lath at different strain amplitudes. Partial transformation from martensite laths to dislocation cells is responsible for the derivation from ideal Masing behavior. In the SEM examination of fracture surfaces, transgranular cracks initiate on the sample surface. Striations can be found during the crack propagation stage.

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    Precipitation Behavior of σ Phase in Ultra-Supercritical Boiler Applied HR3C Heat-Resistant Steel
    Tie-Shan Cao, Cong-Qian Cheng, Jie Zhao, Hui Wang
    Acta Metallurgica Sinica(English letters), 2019, 32 (11): 1355-1361.  DOI: 10.1007/s40195-019-00878-3
    Abstract   HTML   PDF (1419KB) ( 27 )

    The precipitation kinetics of σ phase in commercial HR3C heat-resistant steel during aging at 650-800 °C was studied in the paper. Through morphology, composition and structural analyzing on the second phase in the HR3C steel, it was confirmed that the precipitations after aging were mainly NbCrN, M23C6 and FeCr type σ phase. The time-dependent mass change of the three precipitated phases showed that the linearly increased σ phase after aging at 750 °C-2000 h was transformed from NbCrN phase or M23C6 phase. According to the calculation on the volume fraction of electrolytically dyed σ phase, the time-temperature transformation (TTT) curve for σ phase at 1 vol% in two kinds of commercial HR3C steel (different in grain size) was obtained and analyzed. The nose of the TTT curve was located at around 750 °C for the two kinds of HR3C steel, and the larger grain size HR3C steel displayed a inhibit effect on the precipitation of σ phase. The impact energy of the HR3C steel after aging at 700 °C decreased obviously with the fracture mechanism changing from ductile fracture to intergranular brittle fracture, which was considered to be related to the density of σ-brittle phase after aging.

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    Texture Evolution, Formability and Ridging Resistance of a Sn-bearing Ferritic Stainless Steel Under Different Hot Band Annealing Temperatures
    Yang Bai, Tong He, Dan Guo, Xiu-Ting Liu, Fang-Yuan Shao, Yan-Dong Liu
    Acta Metallurgica Sinica(English letters), 2019, 32 (11): 1362-1372.  DOI: 10.1007/s40195-019-00895-2
    Abstract   HTML   PDF (4442KB) ( 20 )

    The microstructure, texture evolution and spatial orientation distribution during cold rolling and the subsequent annealing as well as formability and ridging of a Sn-bearing ferritic stainless steel under different hot band annealing temperatures were investigated. The four hot bands with annealing temperatures of 900, 950, 1000 and 1050 °C were all cold-rolled to 80% reductions and then were annealed at the same temperature of 900 °C. The results show that optimizing hot band annealing process is beneficial to reduce the amount of {001} <110> grains and weaken the texture intensity, and thus, to reduce ridging and improve formability. In the present study, the final sheets with hot band annealing temperature of 900 °C possess small and inhomogeneous grains with a large amount of {001} <110> orientations, which deteriorates the formability and increases the ridging. In comparison, the final sheets with hot band annealing temperature of 950 °C are comprised of uniform and equiaxed <111>//ND (ND: normal direction) recrystallized grains with a high texture intensity favorable for the improvement in r value and surface quality. However, when hot band annealing temperature further increases to 1000 and 1050 °C, it shows a sharp decrease in r value and a remarkable increase in ridging as a result of a reduction in γ-fiber texture intensity and an increase in grain size in the final sheets. Suitable controlling and optimizing hot band annealing process is essential to improve the formability and reduce the ridging.

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    Corrosion Inhibition of X80 Steel in Simulated Marine Environment with Marinobacter aquaeolei
    M. Saleem Khan, Dake Xu, Dan Liu, Yassir Lekbach, Ke Yang, Chunguang Yang
    Acta Metallurgica Sinica(English letters), 2019, 32 (11): 1373-1384.  DOI: .10.1007/s40195-019-00912-4
    Abstract   HTML   PDF (3449KB) ( 21 )

    In the present study, a novel bacterium (Marinobacter aquaeolei) was examined for its corrosion inhibiting behaviour against X80 pipeline steel. Electrochemical results showed that X80 steel immersed in the solution inoculated with M. aquaeolei possessed very high corrosion resistance compared to that of abiotic control. Besides, scanning electron microscopy, confocal laser scanning microscopy and energy-dispersive X-ray spectroscopy were employed to analyse the corrosion product and the biofilm formed on the metal surface. Fourier-transform infrared spectroscopy was also applied to determine the composition of extracellular polymeric substances (EPS). Above results indicated that the corrosion inhibition efficiency observed in biotic medium was very high (91%), proving that M. aquaeolei was an effective inhibitive agent for the corrosion of carbon steel. The inhibition was credited to the formation of bacterial biofilm and the compact protective layer of the secreted EPS. Thus, this study will introduce a natural, environmentally friendly and cost-effective system for the corrosion control of the carbon steel.

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    Improving Joint Morphologies and Tensile Strength of Al/Mg Dissimilar Alloys Friction Stir Lap Welding by Changing Zn Interlayer Thickness
    Jinglin Liu, Shiyu Niu, Rong Ren, Shude Ji, Lei Wang, Zan Lv
    Acta Metallurgica Sinica(English letters), 2019, 32 (11): 1385-1395.  DOI: 10.1007/s40195-019-00937-9
    Abstract   HTML   PDF (3871KB) ( 24 )

    The pure Zn foils with different thicknesses (0.02, 0.05, 0.1, 0.2 and 0.3 mm) were selected as interlayers to improve the quality of friction stir lap welding joint of 7075-T6 Al and AZ31B Mg dissimilar alloys. The effects of the interlayer thickness on joint formation, microstructure and tensile strength were analyzed. The results displayed that the maximum length of the boundary between stir zone (SZ) and thermo-mechanically affected zone in lower plate was obtained by the addition of the Zn interlayer with 0.05 mm thickness. The Mg-Zn intermetallic compounds (IMCs) were discontinuously distributed in the SZ, replacing the continuous Al-Mg IMCs. The size of Mg-Zn IMCs increased with the increase in the thickness of the Zn interlayer. The maximum tensile shear strength of 276 N mm-1 was obtained by the addition of 0.05 mm Zn foil, which increased by 45.6% of that of the joint without the Zn foil addition.

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    Numerical Simulation of Macrosegregation Caused by Thermal-Solutal Convection and Solidification Shrinkage Using ALE Model
    Kang-Xin Chen, Hou-Fa Shen
    Acta Metallurgica Sinica(English letters), 2019, 32 (11): 1396-1406.  DOI: 10.1007/s40195-019-00897-0
    Abstract   HTML   PDF (2435KB) ( 14 )

    Solidification shrinkage has been recognized as an important factor for macrosegregation formation. An arbitrary Lagrangian-Eulerian (ALE) model is constructed to predict the macrosegregation caused by thermal-solutal convection and solidification shrinkage. A novel mesh update algorithm is developed to account for the domain change induced by solidification shrinkage. The velocity-pressure coupling between the non-homogenous mass conservation equation and momentum equation is addressed by a modified pressure correction method. The governing equations are solved by the streamline-upwind/Petrov-Galerkin-stabilized finite element algorithm. The application of the model to the Pb-19.2 wt%Sn alloy solidification problem is considered. The inverse segregation is successfully predicted, and reasonable agreement with the literature results is obtained. Thus, the ALE model is established to be a highly effective tool for predicting the macrosegregation caused by solidification shrinkage and thermal-solutal convection. Finally, the effect of solidification shrinkage is analyzed. The results demonstrate that solidification shrinkage delays the advance of the solidification front and intensifies the segregation.

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    Optimal Design of Co/In/Cu Sputtering Target Assembly Using Finite Element Method and Taguchi Method
    Lin Jiang, Liang Zhang, Zhi-Quan Liu
    Acta Metallurgica Sinica(English letters), 2019, 32 (11): 1407-1414.  DOI: 10.1007/s40195-019-00875-6
    Abstract   HTML   PDF (1271KB) ( 14 )

    Target assembly is a key consumable material for producing thin film used in the electronic packaging and devices. The residual stresses induced during the process of soldering are detrimental to the performance of target assembly. In this work, the intensity and distribution of the soldering residual stress of Co/In/Cu target assembly subjected to a 20 W/(m2 K) cooling condition corresponding to the actual air cooling process were studied, based on finite element simulation and Taguchi method, to optimize the sputtering target assembly. Effects of different control factors, including solder material, thickness of solder layer, target and backing plate, on the soldering residual stress of target assembly are investigated. The maximum residual stress is calculated as 9.28 MPa in the target located at 0.16 mm from target-solder layer interface and at a distance of 0.78 mm from symmetry axis. The optimal design in target assembly has the combination of indium solder material, cobalt target at 12 mm thick, solder layer at 0.8 mm thick, copper backing plate at 15 mm thick. Moreover, solder material is the most important factor among control factors in the target assembly.

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    Single Crystal Castability and Undercoolability of PWA1483 Superalloy
    De-Xin Ma, Fu Wang, Jian-Zheng Guo, Wen-Liang Xu
    Acta Metallurgica Sinica(English letters), 2019, 32 (11): 1415-1420.  DOI: 10.1007/s40195-019-00891-6
    Abstract   HTML   PDF (1429KB) ( 20 )

    Both of the single crystal (SX) castability and undercoolability of PWA1383 superalloy were investigated during the directional solidification and isothermal cooling. In all the six SX parts of a casting cluster, no stray grains were found, revealing a defect-free SX structure. This excellent SX castability of the superalloy was attributed to its good undercoolability. The melting point (TL) and the critical nucleation temperature (TN) of the alloy were measured to be 1327 °C and 1306 °C, respectively. The statistic average of the critical nucleation undercooling ΔTN?=?TL?-?TN of the alloy was determined to be about 21 K, exhibiting a relatively great capacity to be deeply cooled to a temperature below the melting point without the onset of solidification.

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    Corrosion Resistance and Electrochemical Behaviour of Amorphous Ni84.9Cr7.4Si4.2Fe3.5 Alloy in Alkaline and Acidic Solutions
    Chao Han, Ying-Hua Wei, Hai-Feng Zhang, Zheng-Wang Zhu, Jing Li
    Acta Metallurgica Sinica(English letters), 2019, 32 (11): 1421-1436.  DOI: 10.1007/s40195-019-00904-4
    Abstract   HTML   PDF (7959KB) ( 14 )

    In this work, the corrosion behaviours of the amorphous Ni84.9Cr7.4Si4.2Fe3.5 alloy and its crystalline counterpart are studied in acidic, neutral, and alkaline solutions by scanning electron microscopy, electrochemical impedance spectroscopy, and potentiodynamic and potentiostatic polarization tests. X-ray photoelectron spectroscopy and scanning Kelvin probe are employed to characterize the alloy surface. The results show that the amorphous Ni84.9Cr7.4Si4.2Fe3.5 alloy presents a better corrosion resistance compared to its crystalline counterpart, which is attributed to the uniform energy distribution of the atoms on the amorphous alloy surface, and this presents as a uniform electric potential map to effectively suppress the occurrence of the corrosion cell reaction.

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CN: 21-1315/TG
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