Started in 1988 Monthly
ISSN: 1006-7191
CN: 21-1361/TG
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China Association for Science and Technology
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The Chinese Society For Metals
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Institute of Metal Research, Chinese Academy of Science

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Silver Dopant-Induced Effect on Structural and Optoelectronic Properties of CdSe Thin Films
Jagdish Kaur, Ramneek Kaur, S. K. Tripathi
Acta Metallurgica Sinica(English letters)    2019, 32 (5): 541-549.   DOI: 10.1007/s40195-018-0824-3
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Thin films of CdSe and silver (Ag)-doped CdSe have been prepared on glass substrates by thermal evaporation in argon gas atmosphere. X-ray diffraction pattern indicates the presence of hexagonal structure with preferred orientation along (100) plane. Elemental composition of the thin films has been analyzed using energy dispersive X-ray analysis. Scanning electron microscopy has been used to investigate the morphology of the thin films. Transmission electron microscope reveals spherical nature of nanoparticles. A decrease in the band gap due to the formation of band tails in the band gap with increase in Ag doping in CdSe lattice has been observed. Photoluminescence spectra indicate redshift in band edge emission peak with increase in Ag doping in CdSe. Electrical conductivity measurements are also studied, and two types of conduction mechanisms taking part in the transport phenomena are observed. Hall measurements indicate n-type behavior of undoped and Ag-doped CdSe thin films.

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Microalloying Effect of Sn on Phase Transformation During Heat Treatment in Mg-Y-Zn-Zr Alloys
Pei-Lin Zhang, Yu-Hong Zhao, Ruo-Peng Lu, Zhi-Bing Ding, Hua Hou
Acta Metallurgica Sinica(English letters)    2019, 32 (5): 550-558.   DOI: 10.1007/s40195-018-0826-1
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The microstructure and mechanical properties of the as-cast and heat-treated Mg-4.6Y-2.5Zn-0.6Zr-xSn (x = 0, 0.2 and 0.5 wt%) alloys were investigated in this work. The results showed that the eutectics have been refined with 0.2% Sn addition and it has no effect on the phase category of the alloys. However, Sn3Y5 phase was found in 0.5% Sn-added alloy. After heat treatment at 520°C, the transformation of the long-period stacking ordered (LPSO) phase takes place in the Mg-Y-Zn-Zr alloy, but the transition is not completed in the alloys containing Sn. In addition, during the heat treatment, the mechanical properties of Sn-free alloys are significantly improved, and the strength of alloys containing Sn does not change much. Through observation and analysis of the microstructure and mechanical properties, it is found that Sn addition hinders the process of α′-Mg→α-Mg+14H and the process is the key to the transition of 18H-LPSO to 14H-LPSO.

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Effect of Al on Expansion Behavior of Mg-Al Alloys During Solidification
Yi Meng, Jian Sun, Lei-Gang Cao, Yue Yang, Hai-Tao Zhang, Jian-Zhong Cui
Acta Metallurgica Sinica(English letters)    2019, 32 (5): 559-565.   DOI: 10.1007/s40195-018-0780-y
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The cooling curves and the change of contraction/expansion during solidification and cooling were tested by using a self-made device which could achieve the one-dimensional contraction instead of three-dimensional contraction of the casting. Then, the effects of Al content (0, 1.1, 3, 5, 10, 12.9, 15, 17, 19, 22, 24 and 30 wt%) on the thermal contraction/expansion of the binary Mg-Al as-cast alloys during solidification were obtained. The results showed that expanding instead of contraction was present in Mg-Al alloys with the addition of 0-30 wt% Al during solidification. The values of expansion significantly increased at first and then decreased with the increase in Al content. And the maximum expansion ratio of 0.44% (maximum expansion value: 0.841 mm) was present in the Mg-15 wt% Al alloy. Contraction instead of expansion occurred once the temperature drops to the temperature corresponding to the expansion value in total, indicating the occurrence of a continuous expansion during the solidification process in mushy zone for the Mg alloys with Al addition of 5-30 wt%. The expansion value in total consisted of two parts: the expansions occurring in the liquid-phase zone and mushy zone. The expansion in liquid zone was present in every Mg-Al alloy, and it contributed to the most proportion of the total expansion value when the Al content in Mg-Al alloy was lower than 10 wt% or higher than 22 wt%. However, the total expansion value was mainly determined by the solidification behavior in mushy zone when the Al content was among 10-22 wt% in Mg-Al alloys.

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Formation of Vacancy-Type Dislocation Loops in Hydrogen-Ion-Implanted Fe-Cr Alloy
Yu-Feng Du, Li-Juan Cui, Wen-Tuo Han, Fa-Rong Wan
Acta Metallurgica Sinica(English letters)    2019, 32 (5): 566-572.   DOI: 10.1007/s40195-018-0807-4
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Fe-10 at.%Cr alloy was implanted with hydrogen ions at room temperature, followed by annealing at high temperatures. The annealing process made the defects develop into large dislocation loops. The nature of the dislocation loops formed after annealing was studied by the evolution of loops under in situ electron irradiation in high-voltage electron microscope. It indicated that only interstitial-type loops were observed when annealed at 550 °C and below, but vacancy-type loops started to form at the temperature higher than 600 °C. According to the previous study of our group, the presence of chromium element made the formation temperature of vacancy-type loops higher than that in pure iron. The effect of alloying elements on the formation temperature of the vacancy-type loops was discussed.

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Thermal Conductivity and Tensile Properties of Carbon Nanofiber-Reinforced Aluminum-Matrix Composites Fabricated via Powder Metallurgy: Effects of Ball Milling and Extrusion Conditions on Microstructures and Resultant Composite Properties
Fumio Ogawa, Shuji Yamamoto, Chitoshi Masuda
Acta Metallurgica Sinica(English letters)    2019, 32 (5): 573-584.   DOI: 10.1007/s40195-018-0811-8
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Carbon nanofiber (CNF)-reinforced aluminum-matrix composites were fabricated via ball milling and spark plasma sintering (SPS), SPS followed by hot extrusion and powder extrusion. Two mixing conditions of CNF and aluminum powder were adopted: milling at 90 rpm and milling at 200 rpm. After milling at 90 rpm, the mixed powder was sintered using SPS at 560 °C. The composite was then extruded at 500 °C at an extrusion ratio of 9. Composites were also fabricated via powder extrusion of powder milled at 200 rpm and 550 °C with an extrusion ratio of 9 (R9) or 16 (R16). The thermal conductivity and tensile properties of the resultant composites were evaluated. Anisotropic thermal conductivity was observed even in the sintered products. The anisotropy could be controlled via hot extrusion. The thermal conductivity of composites fabricated via powder extrusion was higher than those fabricated using other methods. However, in the case of specimens with a CNF volume fraction of 4.0%, the thermal conductivity of the composite fabricated via SPS and hot extrusion was the highest. The highest thermal conductivity of 4.0% CNF-reinforced composite is attributable to networking and percolation of CNFs. The effect of the fabrication route on the tensile strength and ductility was also investigated. Tensile strengths of the R9 composites were the highest. By contrast, the R16 composites prepared under long heating duration exhibited high ductility at CNF volume fractions of 2.0% and 5.0%. The microstructures of composites and fracture surfaces were observed in detail, and fracture process was elucidated. The results revealed that controlling the heating and plastic deformation during extrusion will yield strong and ductile composites.

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Effect of pH on the Electrochemical Behaviour and Passive Film Composition of 316L Stainless Steel
Zhu Wang, Zi-Qiang Zhou, Lei Zhang, Jia-Yuan Hu, Zi-Ru Zhang, Min-Xu Lu
Acta Metallurgica Sinica(English letters)    2019, 32 (5): 585-598.   DOI: 10.1007/s40195-018-0794-5
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The effect of pH on the electrochemical behaviour and passive film composition of 316L stainless steel in alkaline solutions was studied using electrochemical measurements and a surface analysis method. The critical pH of 12.5 was found for the conversion from pitting corrosion to the oxygen evolution reaction (OER). OER was kinetically faster than pitting corrosion when both reactions could occur, and OER could postpone pitting corrosion. This resulted in pitting being initiated during the reversing scan in the cyclic polarization at the critical pH. According to the X-ray photoelectron spectroscopy analysis, the content of Cr and Mo decreased with pH, while Fe content increased. This induced the degradation of the passive film, which resulted in the higher passive current densities under more alkaline conditions. The selective dissolution of Mo at high pH was found, which demonstrated that the addition of Mo in austenitic stainless steels might not be beneficial to the corrosion resistance of 316L in strong alkaline solutions.

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Hot Corrosion Behavior of SiO2-Al2O3-Glass Composite Coating on Ti-47Al-2Cr-2Nb Alloy: Diffusion Barrier for S and Cl
Wen-Bo Li, Lan-Lan Liu, Ying-Fei Yang, Sheng-Long Zhu, Fu-Hui Wang
Acta Metallurgica Sinica(English letters)    2019, 32 (5): 599-606.   DOI: 10.1007/s40195-018-0842-1
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Type I hot corrosion behavior of SiO2-Al2O3-glass composite coating based on Ti-47Al-2Cr-2Nb substrate was investigated in the mixture salt of 25 wt%NaCl + 75 wt%Na2SO4 at 850 °C. The results showed that there was a bidirectional ion exchange between composite coating and the film of mixed salts, and the sodium ion in the molten salts penetrated into the glass matrix of composite coating, while the potassium ion in the glass matrix dissolved into the molten salts. A decrease in hot corrosion rate was achieved for the coated alloy in comparison with the bared substrate due to the composite coating acting as a diffusion barrier to sulfur and chlorine and preventing the molten salts from diffusing to the coating/alloy interface during the hot corrosion exposure. Additionally, the composite coating decreased the oxygen partial pressure at the coating/alloy interface and promoted the selective oxidation of Al to form a protective Al2O3 layer.

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Corrosion Behavior of High-Strength Steel for Flexible Riser Exposed to CO2-Saturated Saline Solution and CO2-Saturated Vapor Environments
Da-Zheng Zhang, Xiu-Hua Gao, Lin-Xiu Du, Hong-Xuan Wang, Zhen-Guang Liu, Ning-Ning Yang, R. D. K. Misra
Acta Metallurgica Sinica(English letters)    2019, 32 (5): 607-617.   DOI: 10.1007/s40195-018-0825-2
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The corrosion behavior of high-strength steel used for flexible riser exposed to CO2-saturated saline solution and CO2-saturated vapor environments was studied through immersion experiment and electrochemical corrosion experiment. The corrosion behavior and mechanism of the tested steel were analyzed on the basis of corrosion kinetics, nature of corrosion products, corrosion product morphology, elemental distribution and polarization curves. The experimental results showed that the microstructure of the tested steel was bainitic microstructure. The corrosive activity of the tested steel exposed to CO2-saturated vapor environment was significantly lower than that exposed to CO2-saturated saline solution environment. On prolonging the exposure time, the corrosion rate gradually decreased, the corrosion heterogeneity increased, and the dimensions of FeCO3 crystals gradually became small. At later stages of corrosion, the corrosion current density decreased significantly and the anodic Tafel slope increased, indicating that the corrosion process was strongly inhibited. The corrosion mechanism of low-alloy steel with bainitic microstructure was proposed based on experimental results.

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Numerical Investigation on Residual Stresses of the Safe-End/Nozzle Dissimilar Metal Welded Joint in CAP1400 Nuclear Power Plants
Wen-Chao Dong, Dian-Bao Gao, Shan-Ping Lu
Acta Metallurgica Sinica(English letters)    2019, 32 (5): 618-628.   DOI: 10.1007/s40195-018-0803-8
Abstract   HTML PDF (2810KB)  

The residual stress evolution in a safe-end/nozzle dissimilar metal welded joint of CAP1400 nuclear power plants was investigated in the manufacturing process by finite element simulation. A finite element model, including cladding, buttering, post-weld heat treatment (PWHT) and dissimilar metal multi-pass welding, is developed based on SYSWELD software to investigate the evolution of residual stress in the aforementioned manufacturing process. The results reveal a large tensile axial residual stress, which exists at the weld zone on the inner surface, leads to a high sensitivity to stress corrosion cracking (SCC). PWHT process before dissimilar metal multi-pass welding process has a great influence on the magnitude and distribution of final axial residual stress. The risk of SCC on the inner surface of the pipe will increase if PWHT process is not taken into account. Therefore, such crucial thermal manufacturing process such as cladding, buttering and post-weld heat treatment, besides the multi-pass welding process, should be considered in the numerical model in order to accurately predict the distribution and the magnitude of the residual stress.

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Comparative Study on Solid-State and Metastable Liquid-State Aging for SAC305/Cu Joints
Shuang Li, Xiao-Wu Hu, Wei-Guo Zhang, Yu-Long Li, Xiong-Xin Jiang
Acta Metallurgica Sinica(English letters)    2019, 32 (5): 629-673.   DOI: 10.1007/s40195-018-0789-2
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In order to study the influence of the physical state of solder on the interfacial reaction of dip-soldered Sn-3.0Ag-0.5Cu/Cu system, two kinds of experiments were designed, including: (1) solid-state aging between the solder and Cu substrate; (2) liquid-state aging between the metastable supercooled liquid-state solder and Cu substrate. The aging times were 30, 60, 120 and 180 min, respectively, and the aging temperature was 8 °C lower than the melting point of the Sn-3.0Ag-0.5Cu (SAC305) alloy (217 °C). The experimental data revealed that the physical state of the solder obviously affected the formation of the intermetallic compound (IMC), and resulted in the difference in the diffusion of atoms on the interface between the SAC305 solder and Cu substrate. The IMC interface after aging for 30 min presents unique characteristics compared with that of the sample after dip soldering. The IMC interface of solid-state aged SAC305/Cu couple is relatively planar, while the IMC interface under metastable supercooled liquid-state aging conditions presents scallop-like shape.

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Creep Behavior and Life Assessment of a Novel Heat-Resistant Austenite Steel and Its Weldment
Yu Zhang, Hong-Yang Jing, Lian-Yong Xu, Yong-Dian Han, Lei Zhao, Xi-Shan Xie, Qiu-Hua Zhu
Acta Metallurgica Sinica(English letters)    2019, 32 (5): 638-650.   DOI: 10.1007/s40195-018-0822-5
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In the present study, creep activation energy for rupture was obtained as 221-348 kJ/mol for 22Cr15Ni3.5CuNbN due to the precipitation-hardening mechanism. The extrapolation strength of creep rupture time of 105 h at 923 K for 22Cr15Ni3.5CuNbN is more valid (83.71 MPa) predicted by the Manson-Haferd method, which is superior to other commercial heat-resistant steels. The tensile creep tests ranging from 180 to 240 MPa at 923 K were conducted to investigate creep deformation behavior of welded joint between a novel heat-resistant austenite steel 22Cr15Ni3.5CuNbN and ERNiCrCoMo-1 weld metal. Apparent stress exponent value of 6.54 was obtained, which indicated that the rate-controlled creep occurred in weldment during creep. A damage tolerance factor of 6.4 in the weldment illustrates that the microstructural degradation is the dominant creep damaging mechanism in the alloy. Meanwhile, the welded joints perform two types of deformation behavior with the variation in applied stress, which resulted from the different parts that govern the creep processing. Also, the morphology evolution of the fracture surfaces confirms the effects of stress level and stress state.

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Effect of Aging Heat Treatment on the Microstructure and Creep Properties of the Cast Ni-Based Superalloy at Low Temperature
Xiang-Wei Li, Li Wang, Xin-Gang Liu, Yao Wang, Jia-Sheng Dong, Lang-Hong Lou
Acta Metallurgica Sinica(English letters)    2019, 32 (5): 651-658.   DOI: 10.1007/s40195-018-0827-0
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Effect of aging heat treatment on the grain boundary microstructure and creep properties of a cast Ni-based superalloy was investigated. With increasing aging temperature from 750 to 1000 °C, M23C6 carbides along the grain boundaries evolve from fine distributed block, continuous film into the coarse discrete block. Moreover, the M23C6 carbides are mainly enveloped within γ′ layers along grain boundaries during 1000 °C aging. Creep rupture lifetime and elongation at 760 °C and 645 MPa are improved with increasing the aging temperature. In particular, the creep rupture lifetime of the specimens aging at 1000 °C is one order of magnitude higher than that of the specimens aging at 750 °C. The enhancement of ductility induced by the γ′ envelopes plays a significant role in the improvement of creep rupture lifetime.

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Effects of Phosphorus and Iron on Microstructures and Mechanical Properties in NiCrFe-Based Alloys
Xin-Tong Lian, Wen-Ru Sun, Fang Liu, Dan-Dan Zheng, Xin Xin
Acta Metallurgica Sinica(English letters)    2019, 32 (5): 659-667.   DOI: 10.1007/s40195-018-0784-7
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The microstructures and mechanical properties, especially creep properties, of the NiCrFe-based alloys with various contents of phosphorus and iron were investigated. The results showed that the tensile yield strength decreased with increasing iron contents while had no obvious change with the addition of phosphorus. For creep properties, the alloy with 15.8 wt% iron and 0.09 wt% phosphorus possessed the longest creep life (679 h) among all alloys. Only M23C6was formed in the alloys with low phosphorus contents, while both intergranular M3P and M23C6 precipitated with the increment of phosphorus, which enhanced the strength of grain boundary by hindering the movements of dislocations during creep tests. The reasons for the enhancement of creep life were mainly related to the solid solution strengthening effect of phosphorus and optimization of grain boundary precipitations by phosphorus.

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Retraction Note to: Experimental and Quantum Studies on Adsorption and Corrosion Inhibition Effect on Mild Steel in Hydrochloric Acid by Thiophene Derivatives
M. Yadav, Debasis Behera, R. R. Sinha, P. N. Yadav
Acta Metallurgica Sinica(English letters)    2019, 32 (5): 668-668.   DOI: 10.1007/s40195-018-0835-0
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Quasi-In-Situ EBSD Observation of the Orientation Evolution in Polycrystalline Tantalum During Rolling Deformation
Ya-Hui Liu, Shi-Feng Liu, Chao Deng, Hai-Yang Fan, Qing Liu
Acta Metallurgica Sinica(English letters)    2019, 32 (8): 1015-1020.   DOI: 10.1007/s40195-019-00885-4
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The evolution of crystallographic orientation of polycrystalline tantalum (Ta) during rolling was characterized by electron backscatter diffraction technique in a quasi-in-situ way, and the microstructure and microtexture before and after the deformation were characterized and analyzed, respectively. In the specimen, 164 individual grains were exacted singly from the testing region and their corresponding orientations were reconstructed and analyzed, respectively. Results show that the heterogeneous deformation in a grain can be reflected by the accidented surface microstructure. Moreover, the orientations close to {111} orientations came closer to the {111} corner, while the orientation evolution is more complicated for the orientations close {100} corner, indicating that the evolution of these orientations close to {100} corner seemed to be irregular.

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Microstructure and Its Influence on the Mechanical Properties of Ni-28W-6Cr-Based Alloy-Welded Joints by GTAW
Shuang-Jian Chen, Xiang-Xi Ye, D.K. L.Tsang, Li Jiang, Chao-Wen Li, Kun Yu, Zhi-Jun Li
Acta Metallurgica Sinica(English letters)    2019, 32 (8): 1032-1040.   DOI: 10.1007/s40195-019-00881-8
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Microstructure and mechanical properties of Ni-28W-6Cr alloy-welded joints produced by gas tungsten arc welding were investigated in this work. Results showed that original fine-grain base metal near fusion line totally transformed into coarse heat affected zone after welding. Carbides with different shapes were found in the weld metal and base metal, which all were determined as M6C carbides. In comparison with carbides in base metal, M6C carbides in weld metal are rich in Si and Cr but deficient in W. Moreover, M6C carbides are extremely scarce and hard to be detected in weld metal. Mechanical tests show that the hardness value of weld metal is only about 60% of base metal; the yield strength and tensile strength of welded joint are much lower than those of base metal due to the absence of carbides in weld metal.

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Effect of δ Phase on Microstructure and Hardness of Heat-Affected Zone in TIG-Welded GH4169 Superalloy
Tian-Fu Wang , Xin-Jie Di, Cheng-Ning Li, Jia-Mei Wang, Dong-Po Wang
Acta Metallurgica Sinica(English letters)    2019, 32 (8): 1041-1052.   DOI: 10.1007/s40195-018-0861-y
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The GH4169 superalloy with different content of δ-Ni3Nb phase was welded by tungsten inert gas welding. A detailed study of microstructure and hardness of heat-affected zone (HAZ) was performed in both as-welded and aged state. The results show that the precipitation of δ phase, especially the intergranular δ phase, can lead to the enrichment of Nb and Mo elements, which promote the formation of γ/Laves eutectic constituent at grain boundaries in HAZ. In as-welded state, the hardness decreases first and then increases (exhibiting a “V” shape) with distance away from fusion line in HAZ, which is governed by grain size. After aging treatment, however, the γ″ phase plays a key role in hardness and leads to the “Λ” shape profiles of hardness in HAZ.

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A Novel Series of Refractory High-Entropy Alloys Ti2ZrHf0.5VNbx with High Specific Yield Strength and Good Ductility
Dong-Xu Qiao, Hui Jiang, Wen-Na Jiao, Yi-Ping Lu, Zhi-Qiang Cao, Ting-Ju Li
Acta Metallurgica Sinica(English letters)    2019, 32 (8): 925-931.   DOI: 10.1007/s40195-019-00921-3
Abstract   HTML PDF (2945KB)  

A series of Ti2ZrHf0.5VNbx (x=0, 0.25, 0.5, 0.75 and 1.0) refractory high-entropy alloys were prepared to investigate the alloying effect of Nb on the microstructures and mechanical properties. All the alloys displayed a simple BCC structure. The microstructures of the alloys changed from the initial single-phase columnar structure (x=0) to dendrite microstructure (x>0). At room temperature, all the alloys exhibited high ductility (with the compressive strains of more than 50%). With the increase in Nb content, the yield strength slightly decreased from 1160 to 980 MPa and the hardness dropped from 338 to 310 HV. Moreover, the alloys exhibited low density from 6.47 to 6.84 g/cm3 and high specific yield strength (SYS) from 143 to 179 kPa m3/kg. The comprehensive performance of ductility and SYS was superior to most of the reported high-entropy alloys. The yield strength of the alloys increased from 405 to 859 MPa and from 85 to 195 MPa with the addition of Nb element at 873 K and 1073 K, respectively.

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Hot Deformation Behavior and Hardness of a CoCrFeMnNi High-Entropy Alloy with High Content of Carbon
Yi-Tao Wang, Jian-Bo Li, Yun-Chang Xin, Xian-Hua Chen, Muhammad Rashad, Bin Liu, Yong Liu
Acta Metallurgica Sinica(English letters)    2019, 32 (8): 932-943.   DOI: 10.1007/s40195-019-00916-0
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A CoCrFeMnNi high-entropy alloy with a high content of carbon was synthesized, and its hot deformation behavior was studied at the temperatures 800-1000 °C at the strain rates ranging from 0.001 to 0.1 s-1. As-prepared alloy is a face-centered cubic-structured solid solution, with a large amount of carbides residing at grain boundaries. True stress-strain curves were employed to develop the constitutive equation of apparent activation energy. The apparent activation energy (Q) was found to be 423 kJ mol-1, indicating a dynamic flow softening behavior. The size of dynamic recrystallized (DRXed) grains increases with increasing the temperature or decreasing the strain rate. A processing map was sketched on the basis of the flow stress. The temperature range of 900-1000 °C and 10-3-10-2.6 s-1 strain rate were found to be the optimum hot-forging parameter. With increasing temperature or decreasing strain rate, the volume fraction of fine carbides (≤?1 μm) increases. A lot of coarse carbides can be found in the matrix after deformation at 800 °C, which leads to a high hardness value of 345 HV. The carbides after deformation at 1000 °C are mainly nano-sized M7C3 and M23C6, which can promote the nucleation of DRX.

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A New High-Efficiency Experimental Design for Optimizing Various Flow Velocities Testing in Extremely Aggressive Formation Water
Yang Zhao, Shu-Yun Cao, Tao Zhang, Jun-Feng Xie, Da-Ke Xu, Fu-Hui Wang
Acta Metallurgica Sinica(English letters)    2019, 32 (8): 944-950.   DOI: 10.1007/s40195-019-00919-x
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Compared to the traditional one-by-one method, a new high-efficiency method is used to characterize large numbers of regulations varying samples. Accordingly, bump-shaped electrodes are designed using the computational fluid dynamics model, and the effect of the height and placement of these electrodes is discussed. The experimental feasibility is certified by weight loss measurement. Results indicate that flow velocities of different bump-shaped electrode surfaces are significant differences. Thus, each surface can be analyzed independently; the thickness loss of each electrode surface is consistent with that using one-by-one method, which can effectively improve the experimental efficiency 12 times.

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Microstructural Evolution, Mechanical Properties and Thermal Stability of Gradient Structured Pure Nickel
Xiao Li, Bo Guan, Yun-Fei Jia, Yun-Chang Xin, Cheng-Cheng Zhang, Xian-Cheng Zhang, Shan-Tung Tu
Acta Metallurgica Sinica(English letters)    2019, 32 (8): 951-960.   DOI: 10.1007/s40195-018-00870-3
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The microstructural evolution of pure nickel treated by deep rolling (DR) technique with different indent depths was investigated by means of optical microscopy and transmission electron microscopy. The surface roughness, hardness and residual stress distribution along the depth from surface were measured. Moreover, the DR-treated sample was annealed at temperatures from 300 to 700 °C for 2 h. The results reveal that dislocation movements are the fundamental mechanisms of gradient grain refinement during the DR process. With increasing indent depth of the DR, the gradient microhardness on the cross section of sample significantly increases, the maximum compressive residual stress decreases, and the affecting region of residual stress increases. The results of thermal stability depict that the microstructure can be stable as temperature up to 300 °C, and the abnormal grain growth and annealing twins are observed at 600 °C.

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Effects of Ni Content and Ball Milling Time on the Hydrogen Storage Thermodynamics and Kinetics Performances of La-Mg-Ni Ternary Alloys
Zhen-Yang Li, Sheng-Li Li, Ze-Ming Yuan, Yang-Huan Zhang
Acta Metallurgica Sinica(English letters)    2019, 32 (8): 961-971.   DOI: 10.1007/s40195-019-00879-2
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The effects of Ni content and ball milling time on the hydrogen storage thermodynamics and kinetics performances of as-milled \({\text{La}}_{5} {\text{Mg}}_{95 - x} {\text{Ni}}_{x} \left( {x = 5, \, 10, \, 15} \right)\) ternary alloys have been investigated. The evolution of microstructure and phase of experimental alloys in the absorption/desorption process has been characterized by XRD, SEM and HRTEM. The hydrogen storage kinetics and thermodynamics performances and PCI curves have been tested using the Sievert apparatus. It is found that the rising of Ni content remarkably improves the hydrogen storage kinetic performance, but reduces hydrogen storage capacity. And with the increase in milling time, hydrogen desorption activation (Ea) value decreases firstly and then increases; the minimum value is 47.6 kJ/mol, and the corresponding milling time is 10 h for La5Mg85Ni10 alloy. As for the thermodynamics properties, the hydrogenation enthalpy (ΔH) and hydrogenation entropy (ΔS) both decrease firstly and then increase with the rising of Ni content and milling time. The composite La5Mg85Ni10 alloy milled for 10 h exhibits the best thermodynamics and kinetics performances, the lowest Ea of 47.6 kJ/mol, absorption of 5.4 wt.% within 5 min and desorption of 5.2 wt.% within 3 min at 360 °C and the lowest ΔH and ΔS of 72.1 kJ/mol and 123.2 J/mol/K.

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Effect of Deep Sea Pressures on the Corrosion Behavior of X65 Steel in the Artificial Seawater
Qiu-Shi Li, Shun-Zhong Luo, Xu-Teng Xing, Jing Yuan, Xin Liu, Ji-Hui Wang, Wen-Bin Hu
Acta Metallurgica Sinica(English letters)    2019, 32 (8): 972-980.   DOI: 10.1007/s40195-018-0856-8
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The corrosion behaviors of X65 steel in the artificial seawater at different hydrostatic pressures are investigated by potentiodynamic polarization measurements, electrochemical impedance spectroscopy measurements and weight loss measurements. The corroded morphologies and the corrosion products are also investigated by scanning electron microscopy, X-ray diffraction analysis and Raman analysis. The results show that the corrosion current increases as the hydrostatic pressure increases. The charge transfer resistance decreases as the hydrostatic pressure increases. The corrosion products are mainly composed of γ-FeOOH and Fe3O4 at the atmospheric pressure, while the main components are γ-FeOOH, Fe3O4, and γ-Fe2O3 at the high pressure. The hydrostatic pressure accelerates the corrosion of X65 steel due to its effect on the chemical and physical properties of corrosion products, including the promoted reduction of γ-FeOOH and the wider and deeper cracks on the corrosion products layer.

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Corrosion of New Zirconium Claddings in 500 °C/10.3 MPa Steam: Effects of Alloying and Metallography
Jing-Jing Liao, Zhong-Bo Yang, Shao-Yu Qiu, Qian Peng, Zheng-Cao Li, Ming-Sheng Zhou, Hong Liu
Acta Metallurgica Sinica(English letters)    2019, 32 (8): 981-994.   DOI: 10.1007/s40195-018-0857-7
Abstract   HTML PDF (4054KB)  

With the aim of improving corrosion resistance of rod cladding for in-service and accident conditions, six new zirconium alloys (named N1-N6) have been designed. The contents of Sn and Nb were optimized for better behavior at high-temperature pressurized water, and Fe, Cr, V, Cu or Mo elements were added to the alloys to adjust the corrosion behavior. The current work focused on the rapid corrosion behavior in 500 °C/10.3 MPa steam for up to 1960 h, aiming to test the corrosion resistance at high temperature. The structure of matrix and properties of second-phase particles (SPPs) were characterized to find the main differences among these alloys. All the six alloys exhibited better corrosion resistance than N36, and N1 was shown to have the best performance. A careful analysis of the corrosion kinetics curves revealed that Cr was beneficial for severe condition. Elements Fe, Cr, V, Cu or Mo aggregated into SPPs with different concentrations and structures. This was demonstrated to be the main reason for different corrosion resistance. Due to good processing control, all alloys had a uniform structure and a uniform distribution of SPPs. As for N4, N6 and N36, the existing of large-size SPPs (450 nm) might be a contributing factor of the relatively poor corrosion resistance.

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Effect of Acidified Aerosols on Initial Corrosion Behavior of Q235 Carbon Steel
Miao-Ran Liu, Xiao Lu, Qi Yin, Chen Pan, Chuan Wang, Zhen-Yao Wang
Acta Metallurgica Sinica(English letters)    2019, 32 (8): 995-1006.   DOI: 10.1007/s40195-018-0853-y
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The effect of simulated acidified marine aerosols on the corrosion morphology of carbon steel was studied using an in situ optical stereomicroscope and scanning electron microscope equipped with an energy-dispersive spectrometer and a white-light interferometer. The morphologies of the carbon steel were identified under marine aerosols with different droplet diameters, pH, and acidifications. The results showed that corrosion was initiated in tens of seconds under aerosol droplets acidified by HCl or H2SO4. Despite the differences in the acidifier and diameter, corrosion for acidified droplets with pH?>?2 was general corrosion. For acidified droplets with pH?2SO4. The segregation of Cl- was believed to be the main factor for the formation of the corrosion morphology under acidified droplets with pH?42- in the droplets had some effect on the segregation of Cl- ions when pH?

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Effects of Temperature on Fretting Corrosion Between Alloy 690TT and 405 Stainless Steel in Pure Water
Xing-Chen Liu, Hong-Liang Ming, Zhi-Ming Zhang, Jian-Qiu Wang, Li-Chen Tang, Hao Qian, Yong-Cheng Xie, En-Hou Han
Acta Metallurgica Sinica(English letters)    2019, 32 (12): 1437-1448.   DOI: 10.1007/s40195-019-00929-9
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In pressurized water reactor, fretting corrosion has become the main reason for the failure of 690TT heat exchanger tubes. The effect of temperature on the fretting corrosion behavior between 690TT tube and 405 stainless steel (SS) bar has been studied during 106 fretting cycles. The overall average coefficient of friction (COF) values descends with an increase in test temperature, while the width of worn scar becomes wider. The severest fretting corrosion happens when the test temperature is at 100 °C. The wear mechanism differs at different test temperatures, from adhesive wear at room temperature to abrasive wear and delamination at 100 °C, to abrasive wear at 200 °C. Deformation slips, high residual strain concentration, and micro-cracks are found which are disadvantageous for the further service performance of the tubes.

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Effects of Dissimilar Alumina Particulates on Microstructure and Properties of Cold-Sprayed Alumina/A380 Composite Coatings
Xiang Qiu, Naeem ul Haq Tariq, Lu Qi, Jun-Rong Tang, Xin-Yu Cui, Hao Du, Ji-Qiang Wang, Tian-Ying Xiong
Acta Metallurgica Sinica(English letters)    2019, 32 (12): 1449-1458.   DOI: 10.1007/s40195-019-00917-z
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In this study, alumina/A380 composite coatings were fabricated by cold spray. The influence of alumina particulates’ morphology (spherical and irregular) and content on the deposition behavior of the coatings (including surface roughness, surface residual stress, cross-sectional microstructure and microhardness) was investigated. Results revealed that the spherical alumina mainly shows micro-tamping effect during deposition, which result in remarkable low surface roughness and porosity of the coatings. In addition, very low deposition efficiency and good interfacial bonding between the coating and the substrate were achieved. For irregular alumina particles, the embedding of ceramic particulates in the coating was dominant during deposition process, resulting in high retention in the final deposit. However, it showed limited influence on porosity, surface roughness and interfacial bonding of the deposit. The coatings containing irregular alumina particulates exhibited much higher microhardness than those containing spherical alumina due to the higher load-bearing capacity of deposited alumina.

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Effect of Cl- Concentration on the SCC Behavior of 13Cr Stainless Steel in High-Pressure CO2 Environment
Jin-Jin Zhao, Xian-Bin Liu, Shuai Hu, En-Hou Han
Acta Metallurgica Sinica(English letters)    2019, 32 (12): 1459-1469.   DOI: 10.1007/s40195-019-00923-1
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An effect of Cl- concentration on the stress corrosion cracking (SCC) behavior of 13Cr stainless steel was investigated by employing electrochemical measurements and the slow strain rate tensile tests. These tests were conducted in various solutions with different concentrations of NaCl at 90 °C under 3 MPa CO2 with 3 MPa N2. The results indicate that the passive film of the specimen formed in the 10% NaCl solution has the best protective effect on the matrix. The SCC susceptibility does not increase with increasing the chloride ion concentration, the lowest SCC susceptibility occurs when the NaCl concentration is 10%, and the specimens show higher SCC susceptibility in the 5% NaCl and 20% NaCl solutions.

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Corrosion and Cavitation Erosion Behaviours of Cast Nickel Aluminium Bronze in 3.5% NaCl Solution with Different Sulphide Concentrations
Qi-Ning Song, Nan Xu, Yao Tong, Chen-Ming Huang, Shou-Yu Sun, Chen-Bo Xu, Ye-Feng Bao, Yong-Feng Jiang, Yan-Xin Qiao, Zhi-Yuan Zhu, Zheng-Bin Wang
Acta Metallurgica Sinica(English letters)    2019, 32 (12): 1470-1482.   DOI: 10.1007/s40195-019-00963-7
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The effect of sulphide (Na2S) concentration (SC) on the corrosion and cavitation erosion behaviours of a cast nickel aluminium bronze (NAB) in 3.5% NaCl solution is investigated in this study. The results show that when the SC exceeds 50 ppm, the hydrogen evolution reaction dominates the cathodic process, and a limiting current region appears in the anodic branch of the polarisation curve due to the formation of a copper sulphide film, which is a diffusion-controlled process. After long-term immersion, the increased mass loss rate of NAB with the sulphide additions of 20 and 50 ppm is attributed to the less protective films, which contains a mixture of copper oxides and sulphides. Moreover, NAB undergoes severe localised corrosion (selective phase corrosion, SPC) at the β′ phases and eutectoid microstructure α + κIII. By comparison, NAB undergoes general corrosion and a copper sulphide film is formed in 100 and 200 ppm sulphide solutions. Cavitation erosion greatly increases the corrosion rate of NAB in all solutions and causes a negative potential shift in 3.5% NaCl solution due to the film destruction. However, a positive potential shift occurs in the solutions with SC higher than 50 ppm due to the accelerated mass transfer of the cathodic process. The cavitation erosion mass loss rate of NAB increases with the increase of SC. The occurrence of severe SPC decreases the phase boundary cohesion and causes brittle fracture under the cavitation impact. The corrosion-enhanced erosion is the most predominant factor for the cavitation erosion damage when the SC exceeds 50 ppm.

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Stern-Geary Constant for X80 Pipeline Steel in the Presence of Different Corrosive Microorganisms
Yu-Peng Sun, Chun-Tian Yang, Chun-Guang Yang, Da-Ke Xu, Qi Li, Lu Yin, Cheng-Shuo Qiu, Dan liu, Ke Yang
Acta Metallurgica Sinica(English letters)    2019, 32 (12): 1483-1489.   DOI: 10.1007/s40195-019-00902-6
Abstract   HTML PDF (1585KB)  

The Stern-Geary constant (B value) is indispensable to measure the corrosion rate in the microbiologically influenced corrosion (MIC) systems. Linear polarization resistance (LPR) and weight loss methods were used to study the variation of B values for X80 pipeline steel in the presence of Pseudomonas aeruginosa, Acetobacter aceti and Desulfovibrio vulgaris. The results showed that B values in the presence of three different bacteria were 35.60 ± 0.55 mV, 33.00 ± 1.00 mV and 58.60 ± 0.55 mV, respectively, suggesting that the change of corrosion system significantly affected the B values of X80 pipeline steel. This work further indicated that the determination of B values is necessary to accurately measure the MIC rate by LPR method.

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CN: 21-1315/TG
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