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  • Table of Content
      20 May 2022, Volume 50 Issue 5 Previous Issue    Next Issue
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    Joining and Interface Behavior of Heterogeneous Materials Column
    Research progress in formation mechanism of precursor film at high temperatures
    Lu LIU, Wenqi ZHU, Qiaoli LIN
    2022, 50 (5): 1-10.   DOI: 10.11868/j.issn.1001-4381.2021.000277
    Abstract ( 191 HTML( PDF (10174KB)( 129 Citation

    The formation mechanisms of the precursor film (PF) at high temperature were reviewed, i.e., surface diffusion mechanism, evaporation-condensation mechanism, subcutaneous infiltration mechanism, and rapid absorption then film overflow mechanism. In the experimental metallic systems, the most possible mechanism is the subcutaneous infiltration mechanism, which is related to the apparent contact angle, contact radius, height of gap between the substrate metal and oxide film. In the metal/ceramic system, the formation of precursor film is usually rapid absorption then film overflow mechanism. The appearance of PF for adsorption mechanism needs to meet the contradiction of relative inertia and high affinity at the liquid/solid interface. Meanwhile, another possible mechanism of precursor film in high temperature reactive wetting system, namely film transport mechanism, is introduced. It was pointed out that the difficulty of studying precursor film lies in the unpredictability and instability of precursor film, and its development direction should be systematic, and the corresponding theoretical model should be established.

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    Research progress in microstructure and properties of dissimilar joints of titanium alloy/steel
    Zhe WANG, Mingying XIAO, Huabing GAO, Tao DONG, Haixin LI, Zhenlin YANG, Chunhuan GUO, Fengchun JIANG
    2022, 50 (5): 11-19.   DOI: 10.11868/j.issn.1001-4381.2021.000206
    Abstract ( 126 HTML( PDF (862KB)( 103 Citation

    The study status on the joining of titanium alloy/steel dissimilar joint technology was summarized and reviewed, the microstructure characteristics of titanium alloy/steel direct joining and interlayer joining interface were analyzed.The formation and evolution process of titanium alloy/steel joint interface products with different interlayers (copper, copper-based alloy and others) were emphatically described, and the mechanical properties of titanium alloy/steel with different interlayers and preparation processes were also summarized.Finally, the methods and design ideas that can be adopted for the preparation of good titanium alloy/steel joints were summarized, and it was pointed out that the future development of this field can be combined with simulation in addition to using traditional methods to further the existing research, so as to achieve deeper understanding and experimental prediction.

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    Effect of ultrasonic on friction stir welding formation of aluminum/magnesium dissimilar alloys
    Tao WANG, Chuansong WU
    2022, 50 (5): 20-34.   DOI: 10.11868/j.issn.1001-4381.2021.000597
    Abstract ( 92 HTML( PDF (55569KB)( 66 Citation

    The friction stir butt joint process experiment of 6061 aluminum alloy/AZ31B magnesium alloy plate with thickness of 4 mm was carried out. The material flow in transverse cross-section and horizontal-section, the thickness of the intermetallic compound layers, the mechanical interlocking, and the tensile properties of conventional friction stir welding (FSW) and ultrasonic vibration enhanced friction stir welding (UVeFSW) were compared and analyzed. The action mechanism of ultrasonic vibration was explored. The results show that ultrasonic vibration can promote material flow and heat transfer in different parts of the joint, thereby reduce or even eliminate weld defects. When ultrasonic vibration is applied, the intermetallic compound layer at the aluminum/magnesium interface is thinned, and the mechanical interlocking on the interface is enhanced, so the tensile strength of the UVeFSW joints is improved compared to the FSW joint under the same process parameters. The maximum tensile strength of the UVeFSW joints reaches 174.20 MPa.

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    Influence mechanism of thermoelectric coupling on microstructure of aluminum/steel continuous drive friction welding joints
    Changqing ZHANG, Shuwen WANG, Dechun LUO, Wenchen SHI, Xiao LIU, Guosheng CUI, Boyang CHEN, Zhou XIN, Zhiyuan RUI
    2022, 50 (5): 35-42.   DOI: 10.11868/j.issn.1001-4381.2021.000296
    Abstract ( 58 HTML( PDF (18773KB)( 60 Citation

    Continuous drive friction welding technology was used to weld pure aluminum 1060/Q235 low carbon steel dissimilar material joints, and two cycles (30 d/60 d) thermoelectric coupling test (static load 392 N +high temperature 300 ℃+DC 60 A) was carried out. The effect of thermoelectric coupling on the microstructure, mechanical properties and interface growth of the welded joints of aluminum/steel dissimilar materials was studied. The results show that the thickness of the intermetallic compounds (IMCs) layer in the radial direction of the original joint interface is uneven, and there is no obvious IMCs formation in the central area. After 30 days of thermoelectric coupling, an IMCs layer with a width of 0.3-0.5 μm at the center of the interface is formed and dispersed from the steel side to the aluminum side in granular form, the overall tensile fracture is in the thermally affected zone of the aluminum base metal. After 60 days of thermoelectric coupling, a corrosion groove appears between the IMCs layer and the steel side, and the IMCs are broken, there are no cracks on the steel side, a large number of cracks and voids from the IMCs layer to the aluminum base metal are formed on the aluminum side, segregation of components occurs at the weld and crack tip, the overall tensile fracture is at the weld. The speed of interfacial corrosion and failure rate is proportional to the thickness of the interface IMCs layer, namely vcenter < v1/2R < v2/3R. Due to the uneven structure of the original joint interface and the difference in the growth rate of the structure at different positions of the interface during the thermoelectric coupling test, the boundary line of different fracture morphologies appears at the 2/3R position of the joint interface after thermoelectric coupling. The inner side of 2/3R is dominated by quasi-cleavage fracture, and the outer side of 2/3R is the combined result of dimple fracture and quasi-cleavage fracture.

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    Interfacial microstructure evolution, growth kinetics and mechanical properties of Fe/Al dissimilar metal joints
    Peng LI, Cunzhu ZOU, Honggang DONG, Baosheng WU, Chao LI, Yuesen YANG, Dejun YAN
    2022, 50 (5): 43-51.   DOI: 10.11868/j.issn.1001-4381.2021.000694
    Abstract ( 63 HTML( PDF (7032KB)( 84 Citation

    The interfacial microstructure evolution, growth kinetics of the intermetallic compound (IMC) and mechanical properties of Fe/Al dissimilar metal joints were investigated by vacuum diffusion bonding. The results show that there is no IMC formed on the interface of the joint bonded at temperature of 550 ℃. When the bonding temperature exceeds 575 ℃, the interfacial region is composed of Fe2Al5 and a small amount of FeAl3, and the thickness of IMC layer increases rapidly with the increase of bonding temperature.Under the bonding time of 120 min, the shear strength of the joint increases first and then decreases with the increase of the bonding temperature, and the shear strength of the joint reaches the maximum value of 37 MPa.According to thermodynamic theory, the Gibbs free energy change of Fe2Al5 is the lowest in the range from 550 ℃ to 625 ℃, and then followed by that of FeAl3, and the generated sequence of interfacial IMC can be: Fe2Al5→FeAl3. The interfacial IMC grow in a parabolic manner as a function of bonding temperature, and its growth activation energy is 282.6 kJ·mol-1.The growth rates of IMC at the interface are 1.13× 10-14, 3.59×10-14, 1.21×10-13 m2·s-1 at 575, 600, 625 ℃ respectively.

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    Interfacial microstructure and shear properties of vacuum brazing TiAl alloy/316L stainless steel joint with Zr-Cu-Ni amorphous filler metal
    Yuesen YANG, Honggang DONG, Baosheng WU, Peng LI, Jiang YANG, Yueting MA
    2022, 50 (5): 52-61.   DOI: 10.11868/j.issn.1001-4381.2021.000684
    Abstract ( 56 HTML( PDF (20675KB)( 56 Citation

    Vacuum brazing of TiAl alloy and 316L stainless steel (SS) was conducted using Zr-42.9Cu-21.4Ni amorphous filler metal. The effect of brazing temperature and brazing time on the microstructure and shear properties of the dissimilar metal joints between TiAl alloy and 316L stainless steel was investigated. The results show that the interface of the brazed joint can be divided into six different reaction layers. The microstructure of the brazed joints from TiAl alloy to 316L stainless steel at 1040 ℃/10 min is γ(TiAl)+AlCuTi/α2(Ti3Al)+AlCuTi/AlCu+ZrCuNi+FeZr/Cu8Zr3+ZrCuNi+TiFe+Fe2Zr/FeZr+Fe2Zr+TiFe2+ZrCu/α-(Fe, Cr). With the increase of brazing temperature, the shear strength of brazed joints increase first and then decrease. The maximum shear strength of 162 MPa is obtained at 1040 ℃/25 min. Fracture analysis indicates that cracks initiate at the interface of FeZr+Fe2Zr+TiFe2+ZrCu, and then propagate along Cu8Zr3+ZrCuNi+TiFe+Fe2Zr and α-(Fe, Cr) with cleavage fracture pattern.

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    Review
    Research progress in solid polymer electrolyte-lithium metal anode interface
    Junqiao HUANG, Zhichuan SHEN, Jiawei ZHONG, Wenhao XIE, Zhicong SHI
    2022, 50 (5): 62-77.   DOI: 10.11868/j.issn.1001-4381.2021.000448
    Abstract ( 104 HTML( PDF (16635KB)( 87 Citation

    Solid state lithium battery is expected to be one of the next generation of battery systems with high energy density in the field of high energy. Based on the constructure characteristics and related formation mechanism of interface between solid polymer electrolyte and lithium anode, the impact of interface contact, interface chemistry and electrochemical reaction, and moreover, the growing process of lithium dendrite and other problems on the interface stability and compatibility were systematically discussed in this review.Thus, the application of doping modification, structure design, and other methods for the interfaces between polymer matrix and lithium anode were also emphasized. In addition, the common interface characterization methods and their applications on the interface between solid polymer electrolyte and lithium anode were also reviewed. Finally, based on the relevant strategies of designing and constructing a stable polymer solid electrolyte-lithium anode interface, the development prospects of interface optimization methods such as doping and core layer design were analyzed and prospected in this paper.

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    Research progress in control of microstructure and mechanical properties of in-situ bulk metallic glass composites
    Haimin ZHAI, Xu MA, Huayan YUAN, Mengjing OU, Wensheng LI
    2022, 50 (5): 78-89.   DOI: 10.11868/j.issn.1001-4381.2021.000328
    Abstract ( 87 HTML( PDF (6217KB)( 71 Citation

    Metallic glasses (MGs) have a series of excellent mechanical, physical, chemical and other properties due to their unique short-range ordered and long-range disordered atomic structure characteristics, making them have great potential application value in the field of advanced metal structural materials. However, when the bulk metallic glass (BMG) is deformed under room temperature, the large amount of free volume formed by the shear transformation of the atomic clusters will evolve into a highly localized shear bands. The localized shear bands will undergo instability expansion due to the lack of media, which leads to the fact that BMGs are very prone to brittle fracture at room temperature. In particular, there is no plasticity during uniaxial tension. In order to overcome this shortcoming, the researchers proposed to introduce the micron-sized crystal phase into the glass matrix to suppress the instability expansion of the shear band, so that the in-situ dendritic toughened bulk metallic glass composite (BMGC) has obvious tensile plasticity, and the BMGC has attracted much attention from the material science community. In recent years, researchers have successively improved the plastic deformation ability of BMGC through composition design, preparation technology, heat treatment process and other methods, making BMGC be expected to move towards practical engineering applications. This article focuses on the key scientific issue of microstructure control of in-situ second-phase toughened BMGC, from the factors that affect the microstructure of BMGC (alloy composition design, preparation process parameters, microstructure construction, etc.) to the mechanism of the influence of microstructure on its room temperature mechanical properties, the research results were systematically summarized. In particular, the article focuses on the research progress in the field of in-situ second-phase toughened BMGC in the past 10 years in the field of microstructure regulation and the correlation between mechanical properties at room temperature. In addition, the current problems and challenges in the field of in-situ second-phase toughened BMGC were addressed. The prospects are expected to provide a theoretical reference for the design and preparation of high-strength and high-toughness in-situ second-phase toughened BMGC.

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    Researth progress in preparation of ferrite/polyaniline absorbing composites by in situ polymerization
    Yongtao YU, Yuanjun LIU
    2022, 50 (5): 90-99.   DOI: 10.11868/j.issn.1001-4381.2020.000383
    Abstract ( 94 HTML( PDF (5764KB)( 82 Citation

    Electromagnetic (EM) pollution has become the fourth largest pollution after air pollution, water pollution and noise pollution. Using of EM absorbing materials is an effective way to solve electromagnetic pollution problem, due to their absorption and attenuation characteristics. Polyaniline (PANI), as a kind of resistance loss absorbing material, can meet the development concept of "thin thickness" and "light mass" of absorbing materials. However, its absorbing performance is not ideal due to its poor impedance matching, ferrite, as a kind of traditional magnetic loss-type absorbing material, is limited in its application range due to its high density. The high-density ferrite and low-density polyaniline composite wave-absorbing material can not only adjust the density of the composite material, but also improve the impedance matching, and the wave-absorbing performance of the ferrite/polyaniline composite. In this paper, the preparation methods of polyaniline and ferrite/polyaniline composites were discussed firstly. Secondly, the absorbing mechanism of ferrite/polyaniline composites was expounded. Then, the research progress of composite materials prepared by spinel type, magnetic lead type, garnet type ferrite and polyaniline in the field of wave absorption was summarized, respectively. Finally, the future development directions of ferrite/polyaniline composites were pointed that they should tend to electromagnetic simulation and multi-element composites.

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    Research progress in failure behavior of alloys for hot-section components in thermal power plant boilers under synergism of fireside corrosion and stress
    Xiaofeng YANG, Yaxin XU, Jinyang HUANG, Yingying DANG, Jintao LU, Wenya LI
    2022, 50 (5): 100-111.   DOI: 10.11868/j.issn.1001-4381.2021.000251
    Abstract ( 99 HTML( PDF (5535KB)( 72 Citation

    In response to the China's target of carbon peaking before 2030 and carbon neutralization before 2060, the steam parameters like steam temperature and pressure of thermal power generation need to be further increased to improve its thermal efficiency and reduce carbon emissions, which challenges the safety operation of thermal power plant. It is an important factor that the synergistic effect of high-temperature fireside corrosion and stress leads to the failure of alloys used for boiler, which is quite distinctive from the conventional stress corrosion cracking (SCC) since promising materials such as Ni-based superalloys are not sensitive to SCC tendency under the service condition of fireside corrosion coupled stress. Unfortunately, those impacts are often studied independently. The fireside corrosion mechanism and the stress failure of alloys were summarized in this paper, and the influential factors were pointed out from the materials (metal types, alloy elements and metal surface state) and the environments (temperature, corrosion atmosphere and coal-ash composition) that affect the corrosion performance of alloys. Furthermore, the failure mechanism of alloys from the perspective of the interaction between corrosion and stress was reviewed. On the one hand, the corrosion products deteriorate the creep rupture life of materials; additionally, the defects caused by stress will change the corrosion process of materials. Therefore, this paper focuses on the influence of the synergistic effect of high-temperature fireside corrosion and stress on the material performance, which is indicative for the design and performance of candidate materials for boiler environment of thermal power plants. As an example, the failure of Super304H under the fireside corrosion, creep and the synergism of fireside corrosion and stress were discussed. Finally, the prospect of future investigations on the interaction of fireside corrosion and stress was put forward, including the interaction between fireside corrosion and stress and the failure mechanism of materials under the synergistic effect.

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    Research Article
    Influence of formation process on gas generation and electrochemical performance of Li-rich/Si@C Li-ion batteries
    Xiaoyan SHI, Leilei MA, Zenghua CHANG, Jiantao WANG
    2022, 50 (5): 112-121.   DOI: 10.11868/j.issn.1001-4381.2021.000317
    Abstract ( 72 HTML( PDF (10514KB)( 56 Citation

    According to the unique characteristics of Li-rich manganese-based cathode materials during the first cycle charge, a pulse formation process was designed to reduce the gas production during the formation process and improve the electrochemical performance of the Li-rich/Si@C batteries. The GC-MS, SEM, XPS and electrochemical test results show that, compared with the traditional formation process by optimizing the formation process, the gas production of the batteries under the pulse formation is reduced by about 37%. After pulse formation, a dense film structure can be formed on the surface of the positive and negative active materials, the stress of the cells during the formation process can be relieved. The pulse formation process can also effectively save the formation time, shorten the time from 102.6 h to 81.5 h. In addition, the electrochemical stability during cycle is improved, after 500 cycles, both the capacity retention rate and the median voltage have been significantly improved.

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    Effect of acid treatment on catalytic performance of FeN/ZIF-8 catalyst for oxygen reduction reaction
    Tingxian PAN, Qiuyan ZHENG, Maohui LI, Xin TONG, Changgang HU, Juan TIAN
    2022, 50 (5): 122-129.   DOI: 10.11868/j.issn.1001-4381.2021.000561
    Abstract ( 73 HTML( PDF (5086KB)( 47 Citation

    The development of non-noble metal catalysts with high-performance and low-cost for oxygen reduction reaction is one of the main research directions in proton exchange membrane fuel cells.The catalytic performance of the FeN/ZIF-8 catalysts was investigated using ZIF-8, 1, 10-phenanthroline and FeSO4·7H2O as carbon support, nitrogen and iron precursor, respectively. The effects of acid treatment on structure and catalytic performance of FeN/ZIF-8 catalyst were also explored by various techniques. The structure of catalysts was characterized by X-ray diffraction, specific surface area and pore size distribution measurements and transmission electron microscopy, etc. The catalytic activity and stability of the catalysts for oxygen reduction reaction were investigated by linear sweep voltammetry and accelerated degradation test. The results show that the catalysts with ZIF-8 as the carbon support have high initial catalytic activity for oxygen reduction reaction due to their high specific surface area and the existence of Fe3C in catalysts. The acid treatment can remove some unstable iron-containing carbides and disorder carbon in the catalyst. The structure of the FeN/ZIF-8-A catalyst is modified by acid treatment. The higher specific surface area, more abundant mesoporous structure and higher pore volume, as well as the improved resistance to corrosion in acid solution are the key reasons of FeN/ZIF-8-A catalyst with better catalytic activity and stability for oxygen reduction reaction in acid environment.

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    Failure analysis of chopped carbon fiber SMC composites by micro X-ray computed tomography
    Zijing CHENG, Kaifeng WANG, Lianhong ZHANG
    2022, 50 (5): 130-138.   DOI: 10.11868/j.issn.1001-4381.2020.000765
    Abstract ( 80 HTML( PDF (19511KB)( 59 Citation

    The complex internal three-dimensional fiber distributions and the various microcrack propagation processes of the chopped carbon fiber sheet molding compound (SMC) composites aggravate the difficulty of failure analysis. In-situ micro X-ray computed tomography was proposed in this study to characterize the internal microstructure evolution under different tensile loading conditions. Combined with advanced image acquisition and image processing technologies, the three-dimensional microstructure of the SMC composites, including the complete microcrack propagation, under different loading conditions was reconstructed, where the microcrack geometric size was quantitatively measured. The failure mechanism of the SMC composites was explored via the Tsai-Wu failure criterion and the matrix stress field theory after interface cracking. The proposed method provides an important basis for studying the failure process of the SMC composites and the corresponding failure behavior.

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    Effect of three-directional orthogonal preform weaving parameters on properties of C/C composites
    Qilin DENG, Min YANG, Yumin YAO, Hong LI, Musu REN, Jinliang SUN
    2022, 50 (5): 139-146.   DOI: 10.11868/j.issn.1001-4381.2021.000342
    Abstract ( 47 HTML( PDF (15055KB)( 54 Citation

    Taking the three-directional orthogonal preform with different Z-direction fiber distance as the research object, the carbon/carbon (C/C) composites were prepared by the combination of chemical vapor infiltration and resin impregnation, and the effect of weaving parameters on the microstructure and bending performance of C/C composites were studied. The calculation model was established by taking the smallest repeated structure of three-directional orthogonal preform as a unit, and the relationship between fiber content and weaving parameters of three-directional preform was obtained and verified. The results show that the fiber content of preform is increased with the decrease of Z-direction fiber distance and X, Y-direction fiber layer distance; when the Z-direction fiber distance is increased, the twist deformation of the fiber interweave becomes larger, resulting in the change of the pore structure of the preform; under the same densification process, the change of pore structure affects the composition and distribution of carbon matrix in C/C composites, but has no effect on the morphology of carbon matrix; when the fiber content in X, Y-direction is increased and the distance between fibers in Z-direction is decreased, the flexural strength of the C/C composites is higher.

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    Additive manufacturing process and microstructure during powder extrusion printing of cemented carbides
    Tengxuan LU, Xiaoyan MENG, Shidi LI, Xin DENG
    2022, 50 (5): 147-155.   DOI: 10.11868/j.issn.1001-4381.2021.000803
    Abstract ( 64 HTML( PDF (15224KB)( 55 Citation

    Powder extrusion printing (PEP) is an additive manufacturing (AM) technology based on the combination of traditional metal injection molding and 3D printing, which has the advantages of wide range of printable materials and low cost. The PEP process of WC-13Co cemented carbide was studied, including the development and properties of thermoplastic printing materials, such as the dispersity, rheology and formability. The effects of debinding and sintering process on the microstructure and mechanical properties of the final parts were also investigated. The results show that the specialized binder for PEP of cemented carbides has been prepared successfully. EDS analysis demonstrates that the binder is uniformly dispersed in the green body. The binder can be effectively and totally removed from the green body by two-step debinding process. In combination with vacuum sintering at 1450 ℃ for 60 min, high performance of cemented carbide sample with the shrinkage rate of 17.8%, uniform distribution of WC grain size, and Vickers hardness of 1410HV30 is successfully fabricated. The result confirms that the PEP technology can be applied to prepare cemented carbide materials with high performance and controllable print size, which provides an effective technical route for additive manufacturing of cemented carbide.

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    Microstructure and mechanical property of annealing heat treated AlSi10Mg alloy fabricated by selective laser melting
    Enquan LIANG, Yu DAI, Jing BAI, Yaxiong ZHOU, Dongjian PENG, Qingzheng WANG, Nan KANG, Xin LIN
    2022, 50 (5): 156-165.   DOI: 10.11868/j.issn.1001-4381.2021.000444
    Abstract ( 76 HTML( PDF (38811KB)( 68 Citation

    AlSi10Mg alloy has excellent characteristics such as high specific strength and good wear resistance. The composition of AlSi10Mg alloy is close to the eutectic point, thus it has good forming property and has been widely used in selective laser melting processing. However, for this moment, only the conventional annealing strategy is employed in the selective laser melted AlSi10Mg component, which greatly limits their further applications. In this work, the effects of several annealing on the microstructure and tensile properties of selective laser melted AlSi10Mg alloys were investigated. The results show that the as-fabricated sample presents a mixed structure of columnar α-Al and eutectic Al-Si structure along building direction, which possesses a strong texture of α-Al 〈100〉. The single molten pool consists of fine grain region, coarse grain region and heat affected region. The as-fabricated sample shows ultimate strength of 389.5 MPa with 4% elongation to failure. During the heat treatment, the eutectic Si is broken and spheroidized along with precipitation of supersaturated Al(Si). When the annealing temperature increases from 200 ℃ to 500 ℃, the silicon particle suffers the Ostwald ripening for size increase of 23 times. The samples heat treated at 300 ℃ and 500 ℃ show the ultimate strength of 287.0 MPa and 268.0 MPa, and elongation of 10.3% and 17.2%, respectively.

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    Microstructure and forming control of laser welding-brazing joint of magnesium alloy and steel dissimilar materials
    Yi RONG, Haitao LI, Zhenyu XIONG, Donghai CHENG, Yiping CHEN, Dean HU, De WANG, Zhaoze LIU, Wenjie LI
    2022, 50 (5): 166-171.   DOI: 10.11868/j.issn.1001-4381.2021.000635
    Abstract ( 54 HTML( PDF (9503KB)( 55 Citation

    The laser welding-brazing technology assisted by alternating magnetic field was adapted to AZ31B and Q235. In order to improve the mechanical properties of the joint, Ni interlayer was added to coordinate the metallurgical connection between magnesium alloy and steel, longitudinal alternating magnetic field was applied to optimize the weld forming. The results show that the IMC layer of the joint in fusion welding zone assisted by alternating magnetic field with Ni interlayer is composed of dendrite or continuous nanoscale layered AlNi phase. Magnesium alloy and steel realizes metallurgical connection by laser welding-brazing. The thickness of Fe-Ni solid solution decreases and extends into the weld of magnesium side after the application of alternating magnetic field, and increases the interface bonding area increases by the gully like Fe-Ni solid solution. The actual interface connection length is the main factor affecting the tension shear line load of the joint. The actual interface connection length and the tension shear line load of the welding-brazing joint exhibit first increasing and then decreasing trend as the increase of the magnetic field intensity (B). When the laser power P=1250 W, welding speed v=20 mm·s-1, B=10 mT, frequency f=35 Hz, magnesium alloy and steel are able to achieve the metallurgical connection by the addition of Ni interlayer and the weld forming of the joint is optimized by applying longitudinal alternating magnetic field, the tension shear line load of the joint is the highest, reaching 163 N/mm.

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    First principle calculation of structure and stability of α-Fe/V4C3 interface in vanadium microalloyed steel
    Shuai TANG, Jiamin LIU, Linxian LI, Xiping WEN, Qing PENG, Zhenyu LIU, Guodong WANG
    2022, 50 (5): 172-177.   DOI: 10.11868/j.issn.1001-4381.2021.000278
    Abstract ( 80 HTML( PDF (4447KB)( 55 Citation

    In order to investigate the interface stability of α-Fe/V4C3, the interface structure of three different atomic stacking sequences (Fe-on-C, Fe-on-V and Bridge) of (100)α-Fe/(100)V4C3 were optimized by using the first-principles calculations with pseudo potential plane wave method. The structural stability of α-Fe/V4C3 was measured by the work done of separation for the three configurations. The calculated interfacial separation work of the three configurations is 4.29, 1.43 eV and 2.70 eV, respectively, which larger interfacial separation work indicating stronger interface stability.Therefore, V4C3 precipitated in α-Fe mainly exists in the Fe-on-C configuration, and its interface stability is the strongest. The electronic structure properties of α-Fe/V4C3 were studied by calculating the density of states, differential charge density and electron localization function. The results show that in the Fe-on-C structure configurations, there is a charge-depleted zone for Fe atoms at the interface, and the lost charge transfer to the interface. Due to the strong electronegativity of C atoms, strong mixed ions/covalent bonds are formed at the interface, and the bond and interaction between Fe and C atoms are significantly stronger than that between Fe atoms and V atoms. Meanwhile, according to the total density of states and projected density of states, it is found that the Fe-d orbital and the C-p orbital hybridize in the -4.5 eV to -2.5 eV region, promoting the formation of the Fe—C covalent bond.

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