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

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    , Volume 57 Issue 9 Previous Issue    Next Issue
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    Overview
    Progress on Graphene/Copper Composites Focusing on Reinforcement Configuration Design: A Review
    ZHAO Naiqin, GUO Siyuan, ZHANG Xiang, HE Chunnian, SHI Chunsheng
    Acta Metall Sin, 2021, 57 (9): 1087-1106.  DOI: 10.11900/0412.1961.2021.00120
    Abstract   HTML   PDF (6020KB) ( 928 )

    Copper matrix composites have extensive application prospects in electronics and electrical engineering because of their excellent functional and mechanical properties. Graphene has excellent properties and a two-dimensional structure, making it an ideal reinforcement material. Compared with other reinforcements such as particles and whiskers, graphene has better performance matching with copper. Moreover, its distribution in the copper matrix can be controlled well, which can significantly improve the comprehensive properties of the composite. Therefore, controlling the distribution of graphene using novel fabrication processes is essential. This review focuses on the configuration of graphene distributed in a copper matrix (uniform configuration, layered configuration, and network configuration) and the corresponding fabrication processes. The effects of different graphene configurations on the properties of various copper matrix composites are discussed. New ideas for graphene configuration design, future development trends, and potential applications of graphene/copper matrix composites with unique configurations are anticipated.

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    Current Research Status of Interface of Ceramic-Metal Laminated Composite Material for Armor Protection
    ZHAO Yuhong, JING Jianhui, CHEN Liwen, XU Fanghong, HOU Hua
    Acta Metall Sin, 2021, 57 (9): 1107-1125.  DOI: 10.11900/0412.1961.2021.00051
    Abstract   HTML   PDF (3677KB) ( 1006 )

    A composite material with a laminated structure can be fabricated through layer-by-layer stacking of ceramic and metal in a certain order. It has characteristics of high strength, high hardness, low density of ceramics, and strong ductility of metals; thus, it can be used for bulletproof armor materials. During bullet antipenetration, the ceramic panel is responsible for decelerating and breaking the projectile, and the metal backplate absorbs the kinetic energy of the bullet through plastic deformation, thereby forming a complete bulletproof armor system. However, there are some problems associated with laminated materials, such as the significant difference between the properties of ceramic and metal, weak interface bonding strength, and easy occurrence of tip cracks due to the increase in the internal stress of the impacted material. The ceramic-metal interface easily leads to a sudden change in material properties, and crack propagation and migration affect the properties. After being impacted, cracks first appear in the interlayer, where the interface bonding strength is still unideal, easily leading to a drop between the ceramic panel and metal backplate. In this study, the preparation and observation of interface structure, phase-field simulation of interface fracture, finite element simulation of interface impact resistance, meshless smoothed-particle hydrodynamic method for high-velocity impact and large deformation, and first-principles calculations of interface strength were reviewed. Finally, some suggestions are presented for future development: (1) Strengthening the research of ceramic toughening to enhance the matching degree between the ceramic panel and metal backplate, reducing the sudden change of ceramic to metal performance, and making the performance of ceramic-metal laminated materials more uniform is crucial. In addition, studying metal strengthening is necessary. On the premise of not damaging metal ductility, nano-phases can be added to prepare metal matrix composites for metal strengthening; (2) More multiscale research methods, such as phase-field method, finite element analysis, and first-principles calculations are needed, especially focusing on how to organically and effectively combine these methods. The complementary coupling of multiscale experimental research and computational simulation methods is a powerful tool for the interface design of ceramic-metal laminated materials in the future.

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    Fine-Tuning Weld Metal Compositions via Flux Optimization in Submerged Arc Welding: An Overview
    WANG Cong, ZHANG Jin
    Acta Metall Sin, 2021, 57 (9): 1126-1140.  DOI: 10.11900/0412.1961.2021.00148
    Abstract   HTML   PDF (3272KB) ( 626 )

    Flux is an indispensable consumable for submerged arc welding. Owing to the occurrence of complex chemical reactions between flux (slag), weld pool, and arc plasma, flux plays an essential role in determining the final composition of weld metal. To ensure a sound weldment, understanding how submerged arc welded metal compositions are fine-tuned by flux optimization is necessary. Herein, recent progress regarding the control mechanisms of fluxes on submerged arc welded metal compositions is studied. Particularly, the element transfer behaviors of major elements, including oxygen, silicon, manganese, titanium, and carbon, are documented from thermodynamic perspectives. Salient element transfer features incurred by the application of high heat input welding are interpreted. Moreover, the capabilities and limitations of prevailing compositional prediction models are evaluated. Finally, fundamental challenges to be explored further are discussed.

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    Research Progress on Nb-Si Base Ultrahigh Temperature Alloys and Directional Solidification Technology
    CHEN Ruirun, CHEN Dezhi, WANG Qi, WANG Shu, ZHOU Zhecheng, DING Hongsheng, FU Hengzhi
    Acta Metall Sin, 2021, 57 (9): 1141-1154.  DOI: 10.11900/0412.1961.2021.00163
    Abstract   HTML   PDF (3141KB) ( 492 )

    The Nb-Si base ultrahigh temperature alloys with low density and high melting point is one of the candidate materials for the hot components of next-generation aero-engines. The insufficient of the Nb-Si based ultrahigh temperature alloy at 270-280 K is the bottleneck for its industrial application. Alloying and directional solidification are considered as effective methods for improving the room-temperature fracture toughness. The research progress of the two methods for the Nb-Si-based ultrahigh temperature materials are reviewed herein. In the aspect of alloying, the toughening of the Niobium solid solution (Nbss) phase is mainly conducted by dislocation toughening and phase transformation toughening. The high-temperature performance of the silicide (Nb5Si3) phase can be improved by solid-solution strengthening and phase transformation, and the silicide phase would tend to grow in a near “Y” shape. The interface between the Nbss and silicide phases could be modified. In conclusion, Ti, HF, Zr, B, and Mg can improve the room-temperature fracture toughness of Nb-Si base ultrahigh temperature alloys. The methods and characteristics of the directional solidification of Nb-Si materials are introduced. Herein, the effects of different processing parameters on the phase composition, microstructure morphology, room-temperature fracture toughness, and high-temperature strength of Nb-Si base ultrahigh temperature alloys are summarized. The microstructure evolution and mechanical property strengthening mechanism during directional solidification are reviewed. The well-coupled Nbss/Nb5Si3 unidirectional growing eutectic structure can be obtained by controlling the process. In this condition, the room-temperature fracture toughness could be improved by reducing the Nbss phase thickness and increasing the eutectic structure continuity. The future development of Nb-Si alloying and directional solidification is prospected.

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    Several Issues on the Development of Grain Boundary Diffusion Process for Nd-Fe-B Permanent Magnets
    LIU Zhongwu, HE Jiayi
    Acta Metall Sin, 2021, 57 (9): 1155-1170.  DOI: 10.11900/0412.1961.2020.00438
    Abstract   HTML   PDF (4174KB) ( 795 )

    Nd-Fe-B based permanent magnets have been widely used in many industries, including renewable energy, information and communication, and intelligent manufacturing. The applications in the electric vehicle drive motors and wind power system generators set high requirements on the elevated temperature performance and coercivity for Nd-Fe-B magnets. Heavy rare earth (HRE) of Tb and Dy have been frequently used to substitute Nd to enhance the anisotropy field of the magnets. However, introducing these HRE elements reduces the remanence of magnets and increases the total price of end-products. The grain boundary diffusion (GBD) process, invented at the beginning of this century, is a significant progress in the field of rare earth permanent magnet manufacturing. The coercivity can be significantly improved by diffusing HRE elements or rare earth alloys into the magnet along the grain boundary. Simultaneously, the reduced heavy rare earth consumption and enhanced performance-cost ratio can also be realized. Although the GBD process has attracted much attention and has been quickly industrialized since its appearance, some key issues still exist on technical and theoretical levels. Based on the latest domestic and overseas developments and the research results from the authors' group, this paper summarizes the urgent problems and feasible solutions for the GBD process. Several issues are described in this report, including the GBD process for thick magnets, utilization of anisotropic behavior of GBD, selection of low-cost diffusion sources, combination of GBD with the existing process, influence of GBD on the service performance, and advancement of GBD related theories. The challenges and opportunities in the future development of the GBD process for Nd-Fe-B based magnets are also highlighted.

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    Carrier Mobility Optimization in Thermoelectric Materials
    ZHAO Li-Dong, WANG Sining, XIAO Yu
    Acta Metall Sin, 2021, 57 (9): 1171-1183.  DOI: 10.11900/0412.1961.2021.00130
    Abstract   HTML   PDF (3222KB) ( 832 )

    Thermoelectric (TE) materials are functional materials that can realize the direct and reversible conversion between heat and electricity. Their conversion efficiency is determined by their average figure of merit (ZTave). Generally, high ZTave requires TE materials to possess both excellent electrical transport properties and low thermal conductivity, called “electron crystal-phonon glass.” To date, although commonly used band manipulation and defect designing strategies can optimize the carrier effective mass and lattice thermal conductivity, they reduce the carrier mobility and thus limit the improvement of ZTave. Therefore, maintaining high carrier mobility is essential for improving ZTave over a wide temperature range. In this review, the methods to optimize carrier mobility, including crystal defect manipulations and multiple coupling parameter manipulations, were summarized. Specifically, crystal defect manipulations include strategies of crystal growth, crystal symmetry manipulation, and point defect manipulation, and the multiple coupling parameter manipulations include band alignment strategies, modulation doping, and band sharpening. Further, the applications of these strategies in multiple TE material systems were discussed, such as in SnSe/S, PbTe/Se/S, BiCuSeO, and BiAgSeS compounds. It was proven that the above strategies can well optimize the TE performance over the entire working temperature by effectively balancing carrier and phonon scattering and synergistically manipulating the coupling relationships between carrier mobility, effective mass, and carrier density. The importance of carrier mobility optimization in TE materials and a new research idea for developing high-efficiency TE materials were presented.

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    CMAS Corrosion Behavior and Protection Method of Thermal Barrier Coatings for Aeroengine
    GUO Lei, GAO Yuan, YE Fuxing, ZHANG Xinmu
    Acta Metall Sin, 2021, 57 (9): 1184-1198.  DOI: 10.11900/0412.1961.2021.00121
    Abstract   HTML   PDF (4942KB) ( 767 )

    Thermal barrier coating (TBC) is a core aero-engine turbine blade technology, which can significantly increase an engine's operating temperature, thrust, and working efficiency. Moreover, high-engine operating temperatures make aero-engine turbine blades and their TBCs suffer from severe corrosion of environmental deposits (the main components are CaO, MgO, Al2O3, and SiO2, together referred to as CMAS), causing premature failure. CMAS corrosion has become a key issue that limits the service temperature and lifetimes of TBCs, and its protection has been a research hotspot. In this paper, first, the scholars' understanding of CMAS corrosion to TBCs and the characteristics of CMAS were reviewed. Then, CMAS corrosion mechanisms for TBCs were briefly described. The protection methods of TBCs from CMAS corrosion were elaborated from the aspects of TBC's surface protection layer design, coating component modification, new CMAS-resistant coating materials development, and coating microstructure design. Finally, the application of TBCs in ultrahigh temperature environments and the development direction of corrosion protection were forecasted.

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    Progress in Interfacial Thermodynamics and Grain Boundary Complexion Diagram
    HU Biao, ZHANG Huaqing, ZHANG Jin, YANG Mingjun, DU Yong, ZHAO Dongdong
    Acta Metall Sin, 2021, 57 (9): 1199-1214.  DOI: 10.11900/0412.1961.2021.00036
    Abstract   HTML   PDF (4420KB) ( 811 )

    Grain boundaries (GBs), a crucial component of microstructures, have a significant influence on the properties of materials. The GB complexion (GBC) transitions are essential information to accurately explain numerous material phenomena. However, owing to the complexity of GB structures and the difficulty in observation of GBC transitions, there is still no direct evidence and mechanism explanation for these material phenomena. With the advancement of characterization equipment, especially spherical aberration-correction transmission electron microscopy, coupled with powerful computer simulation, the establishment of interfacial thermodynamic models to construct different types of GBC diagrams, which provide a broad prospect for the study of GB structures and GBC transitions, is essential. In this paper, the progress of interface thermodynamics and GBC diagrams from the aspects of the classification and characterization of GBs and GBC transitions, interface thermodynamic models, and the construction of GBC diagrams were reviewed. The paper also looks forward to the future development of interface thermodynamics and GBC diagrams.

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