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      20 March 2019, Volume 47 Issue 3 Previous Issue    Next Issue
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    GRAPHENE COLUMN
    Structural feature of graphene-like graphitic carbon nitride nanosheets synthesized via high-energy microwave irradiation
    Jing-ye ZOU, Yong-zhi YU, Yong-pan GU, Xia-wei YUE, Jiang MENG, Shu-ping LI, Ji-gang WANG
    2019, 47 (3): 1-7.   DOI: 10.11868/j.issn.1001-4381.2018.000360
    Abstract ( 999 ( PDF (4503KB)( 421 Citation

    Microwave synthesis has many advantages covering rapid, high-efficient, environmentally-friendly etc. Herein, graphene-like carbon nitride nanosheets (g-C3N4-NS) were successfully prepared by high-energy microwave heating method using melamine and carbon fibers as precursor and microwave absorber, respectively. The as-synthesized samples were investigated via various analytic techniques including X-ray diffraction (XRD), field-emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM) and fourier transform infrared spectroscopy (FT-IR). Results show that the g-C3N4-NS sample prepared by microwave heating exhibits the obvious feature of graphene-like ultra-thin nanosheets in comparison with sample synthesized by conventional thermal polycondensation. Meanwhile, compared with graphene-like carbon nitride nanosheets prepared by other approaches including ultrasonic exfoliation and oxidation etching methods, the sample synthesized by microwave heating has smooth, flat and strong rigidity surface.

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    Preparation of graphite modified PDC-SiCNO ceramics and its dielectric properties
    Yu-xi YU, Fan-sen XIA, Qi-fan HUANG
    2019, 47 (3): 8-14.   DOI: 10.11868/j.issn.1001-4381.2017.000662
    Abstract ( 834 ( PDF (3854KB)( 374 Citation

    Graphene ball reinforced SiCNO ceramics (SiCNO-GO) were prepared by using polyvinylsi-lazane (PVSZ) as raw material and graphene oxide (GO) as carbon source and anhydrous ethanol (ETOH) as dispersant. X-ray diffraction (XRD), Raman spectroscopy (Raman), electron spin resonance (EPR) and SEM were used to study the effect of SiCNO-GO ceramics on the dielectric properties. The results show that the microsphere density and particle size of SiCNO-GO ceramics are related to the content of GO. With the increase of GO content in SiCNO-GO ceramics, the dielectric constant and dielectric loss of SiCNO-GO ceramics also increase, reach the maximum value when the GO mass fraction is 0.1%. When the GO mass fraction is 0.3%, the dielectric constant and dielectric loss of the SiCNO-GO ceramics decrease.

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    Mechanical behavior of graphene or SiC reinforced aluminum matrix composites under dynamic loading
    Yu-kai YANG, Bao ZHANG, Xu-dong WANG, Hu-sheng ZHANG, Yue WU, Yong-jun GUAN
    2019, 47 (3): 15-22.   DOI: 10.11868/j.issn.1001-4381.2017.001457
    Abstract ( 944 ( PDF (4757KB)( 407 Citation

    Quasi-static compression experiments on graphene-reinforced aluminum matrix composites were carried out by means of microcomputer controlled electronic universal testing machine, while dynamic behavior of the composites at various high strain rates was determined by split hopkinson pressure bar (SHPB). In addition, scanning electron microscopy (SEM) was employed to examine the morphological feature of aluminum matrix composites reinforced respectively by grapheme and SiC. The results show that at all strain rate, the yield strength of aluminum is improved both with addition of graphene and SiC, by incorporation of graphene, the yield strength of aluminum is improved more significantly, but without affecting the strain hardening rate of the material. In comparison with SiC as reinforcements, use of graphene undermines strain rate sensitivity of the composites, and meanwhile results in a decline in ultimate strength. J-C and Z-A constitutive models were fitted respectively to the experimental results to obtain relative parameters. Comparison between the two models suggests that J-C model is more accurate in terms of describing stress-strain behavior of both composites reinforced respectively by graphene and SiC.

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    Dynamic mechanical behavior of graphene nanoflakes reinforced aluminum matrix composites
    Shuang-zan ZHAO, Shao-jiu YAN, Xiang CHEN, Qi-hu HONG, Xiu-hui LI, Sheng-long DAI
    2019, 47 (3): 23-29.   DOI: 10.11868/j.issn.1001-4381.2017.001177
    Abstract ( 757 ( PDF (6640KB)( 340 Citation

    Graphene nanoflakes (GNFs) reinforced aluminum matrix composites were prepared by compressing-sintering-hot extrusion process, and their compressive properties were tested. The results show that GNFs/Al composites are high strain rate sensitive materials. When the strain rate increases from 10-3s-1 to 3×103s-1, the strength of the composites increases obviously. However, when the strain rate further increases to 5×103s-1, the strength of the composites declines a little due to the internal thermal softening of the material. Dynamic recrystallization occurs in the matrix of the composites after dynamic compression, and the higher the strain rate is, the more significant the dynamic recrystallization is. At the same time, the enhanced phase GNFs remain intact and bonded with matrix in atom scale while undergo a distorted deformation. Therefore, the plasticity of graphene reinforced aluminum matrix composites under dynamic compression is excellent.

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    REVIEW
    Research progress on designing stable and reversible cathodes catalysts for lithium-air batteries
    An-jun HU, Jian-ping LONG, Chao-zhu SHU
    2019, 47 (3): 30-41.   DOI: 10.11868/j.issn.1001-4381.2017.001563
    Abstract ( 730 ( PDF (3498KB)( 484 Citation

    Lithium-air batteries(LABs) are among the most promising electrochemical energy storage technologies in the future due to extremely high theoretical energy density. The performance of LABs is mainly governed by the electrochemical reactions that occur on the surface of the cathode. Therefore, the rational design of a cathode with high stability and reversibility is the key to commercially viable LABs. However, the side reactions are caused by the instability of traditional carbon-based electrodes can limit capacity and cycle performance of LABs, therefore, alternative carbon-based electrode materials are required. Based on the structure and the principle of cathode reaction of LABs, the current challenges of LABs were presented. Then based on the analysis of the instability of carbon-based cathode, the design of a stable and reversible cathode for LABs was summarized. Finally, a perspective that the rational design of the cathode catalyst and the in-depth understanding of the catalytic mechanism play a decisive role in the performance improvement of LABS was provided.

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    Progress in research of polyaniline and its application in camouflage
    Liang ZHAO, Xiao-xia LI, Yu-xiang GUO, De-yue MA
    2019, 47 (3): 42-49.   DOI: 10.11868/j.issn.1001-4381.2016.001580
    Abstract ( 299 ( PDF (1591KB)( 323 Citation

    Polyaniline (PANI) is a kind of conductive polymer, which has some special optical and dielectrical properties due to its specific doping mechanism varied structures. PANI also is easy to combine with other organic or inorganic materials, which extends its function and application. Therefore, PANI is always the research focus of conductive polymers. In this paper, the research progress in the synthesis, characterization, and modification of PANI were reviewed; Then the the characteristics of PANI in the visible, infrared and radar waves were analyzed. At last, PANI research and improvement in molecular structure design, nanomaterial composite, device structure were forecasted, to solve practical difficulties in flexibility, compatibility, longevity, power consumption. The PANI will play an important role in the field of intelligent camouflage such as optical adaptive camouflage and multi-band composite stealth camouflage.

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    Development and applications of micro-arc oxidation technology
    Ren-guo SONG
    2019, 47 (3): 50-62.   DOI: 10.11868/j.issn.1001-4381.2018.000582
    Abstract ( 2035 ( PDF (12957KB)( 1299 Citation

    The development status of micro-arc oxidation (MAO) technology at home and abroad was reviewed. The principle and process characteristics of MAO technology were primarily introduced. The influence factors for the microstructure and properties of MAO ceramic coatings as well as the applications of MAO technology were summarized. Also, the existing problems of MAO technology were analyzed, and it has been pointed out that MAO technology will be developed towards the direction of low energy consumption, treatment of ultra-large and complex light metal components and combining with other surface technologies in the future.

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    RESEARCH ARTICLE
    Synthesis, modulation of electromagnetic properties of FeCo/PPy nanocomposites
    Zhi-ran YAN, Yi-bo AI, Yi-xuan WANG, Yu WANG, Jun HE, Hai-cheng WANG
    2019, 47 (3): 63-70.   DOI: 10.11868/j.issn.1001-4381.2018.000280
    Abstract ( 583 ( PDF (7937KB)( 320 Citation

    In order to improve the impedance matching and wave absorption, FeCo magnetic nanoparticles with different reaction time were synthesized, and after being modified and in-situ oxidation polymerization, FeCo/PPy nanocomposites were prepared. Results show that the FeCo/PPy composites with FeCo nanoparticles which reaction time is 2h possess a maximum reflection loss (RL) value of -38.19dB at 14.45GHz and 2mm thickness with an effective absorption bandwidth (RL ≤ -10dB) of 5.45GHz (12.24-17.69GHz). The introduction of magnetic nanoparticles with polypyrrole can effectively decrease the complex permittivity and improve the impedance matching, which will reduce the reflection of electromagnetic wave. Meanwhile, the multimechanism of magnetic loss, dielectric loss and interface polarization loss, can prompt the absorption to the electromagnetic wave greatly.

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    Effects of iron salts on synthesis of MIL-100(Fe) and photocatalytic activity
    Yu ZHANG, Xiang-yue LIU, Hui-ling MAO, Chen WANG, Xuan DU, Hu CHENG, Jin-liang ZHUANG
    2019, 47 (3): 71-78.   DOI: 10.11868/j.issn.1001-4381.2018.001261
    Abstract ( 1261 ( PDF (3708KB)( 526 Citation

    The iron salts (ferric and ferrous salts) play a critical role for the synthesis of morphology and size controllable, and highly crystalline MIL-100(Fe). The use of ferrous salt results in octahedral, highly crystalline MIL-100(Fe) with high surface areas. In contrast, the use of ferric salt only results in smaller Fe-BTC metal-organic polymers with low crystallinity. The crystal structure, morphology, photo-absorption property, absorption and photocatalytic-degradation properties of MIL-100(Fe) and Fe-BTC toward RhB, were fully characterized by XRD, SEM, FT-IR, UV-Vis DRS, and UV-Vis spectroscopy. The results indicate that the slow oxidation of Fe2+ to Fe3+ is key to the synthesis of highly crystalline MIL-100(Fe) since this process facilitates the formation of μ3-OFe(Ⅲ)O6, which is inorganic secondary building unit (SBU) of MIL-100(Fe). When FeCl3 used as iron source, the fast dynamic reaction of Fe3+ with BTC3- is not beneficial to the formation of μ3-OFe(Ⅲ)O6 SBU; therefore, Fe-BTC nanoparticle polymer is obtained. The smaller size of Fe-BTC nanoparticless, and meso-/macroporous structure in the aggregated nanoparticle surface, which facilitates the diffusion of RhB as well as the photodegradated forms. Fe-BTC shows better absorption capacity and photocatalytic activity toward RhB compared to MIL-100(Fe).

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    Effect of magnetic field on surface characteristics of magnetorheological elastomer
    De-jun REN, Rui LI, Ming-lian WANG, Jiu-shan LIU
    2019, 47 (3): 79-86.   DOI: 10.11868/j.issn.1001-4381.2017.001611
    Abstract ( 777 ( PDF (18180KB)( 260 Citation

    To explore the influence of magnetic field on surface characteristics of magnetorheological elastomers (MREs), the MREs with volume fractions of 5%, 10%, 15%, 20%, 25% and 30% were fabricated. Then the surface observation experiments of metallographic microscope, white light interferometer and sliding friction test were carried out with magnetic field and without magnetic field. The surface observation shows that the surface magnetic particles of the sample are increased with the increase of volume fraction, and the surface roughness of the samples of each component is reduced, with the magnetic field, the ferromagnetic particles of MREs with the volume fraction of 5% is reduced most up to about 20%. The friction experiment results show that the friction coefficient is decreased with the increase of volume ratio and under the application of magnetic field, the 30% of MREs' friction coefficient is reduced by approximately 38% compared to the 5%. The ferromagnetic particle content on the surface of the MRE is a major factor affecting the friction characteristics.

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    Preparation and properties of SiC ceramics via SLS/CIP process
    Peng CHEN, Xiao-gang ZHU, Jia-min WU, Lian-feng WANG, Yu-sheng SHI
    2019, 47 (3): 87-93.   DOI: 10.11868/j.issn.1001-4381.2017.001549
    Abstract ( 743 ( PDF (11681KB)( 399 Citation

    With the spray-dried SiC-Al2O3-Y2O3 powder as raw material, composite powder prepared by mechanical mixing was used to fabricate SiC ceramics by selective laser sintering/cold isostatic pressing combined with liquid phase sintering.The material phase composition, microstructure, flexural strength and density of SiC ceramics were characterized. The results show that spray-dried powder has an average diameter of 39.43μm with fine sphericity and flowability, which is suitable for SLS process. With the optimum parameters (laser power of 7W, scanning speed of 2200mm/s, scanning space of 0.15mm and layer thickness of 0.15mm) and CIP pressure of 80MPa, the green bodies show the superior quality with flexural strength of (2.23±0.10)MPa and bulk density of (1.31±0.05)g/cm3. After being sintered at 1950℃ for 2h, samples are densified that the bulk density and relative density of SiC ceramics are (1.95±0.17)g/cm3 and (60.81±5.31)%, respectively and the flexural strength is (55.43±4.04)MPa.

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    "Necklace" structure of the 4th generation powder metallurgy superalloy after hot deformation
    Qiong HOU, Yu TAO, Jian JIA
    2019, 47 (3): 94-100.   DOI: 10.11868/j.issn.1001-4381.2018.000322
    Abstract ( 902 ( PDF (18063KB)( 298 Citation

    The "necklace" structure of an advanced 4th generation powder metallurgy(PM)superalloy after isothermal forging was investigated by means of scanning electron microscope, transmission electron microscope and electron back scattering diffraction technique. The formation mechanism and elimination method of the "necklace" structure were studied. The results show that after multiple isothermal forging, most region of the forging are fully recrystallized, and equiaxed fine-grained microstructures are obtained. Nevertheless, a typically incomplete recrystallization microstructure, namely the "necklace" structure, is formed nearing the upper and lower end faces of the forging. A great amount of fine recrystallized grains are distributed around the non-equiaxed deformed grains. The deformed grains contain a high density of low angle grain boundaries, so it means plenty of entangled dislocations exist. The samples containing "necklace" structure are annealed over the temperature range from 1080℃ to 1180℃. With the increasing temperature, both the recrystallization volume fraction and recrystallization grain size are increased gradually. The "necklace" structure of the alloy forging is basically eliminated after recrystallization annealing at 1150℃. Therefore, the uniform fine-grained disk can be obtained, which meet the requirements of dual microstructure heat treatment.

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    High temperature tribological properties of laser in-situ synthesized self-lubricating composite coating on Ti6Al4V alloy
    Zhong-yan ZHOU, Su-guo ZHUANG, Xia-hui YANG, Mian WANG, Ying-she LUO, Yu LIU, Xiu-bo LIU
    2019, 47 (3): 101-108.   DOI: 10.11868/j.issn.1001-4381.2018.000849
    Abstract ( 700 ( PDF (10234KB)( 334 Citation

    In order to improve the high temperature tribological properties of Ti6Al4V alloy, multi-phase hybrid metal matrix high-temperature self-lubricating anti-wear composite coating was in-situ synthesized by laser clad with the powder precursor of Ni60-16.8%TiC-23.2%WS2(mass fraction, the same below). The microstructure, phase composition and tribological properties as well as the corresponding wear mechanisms of the composite coating at 20, 300, 600, 800℃ were analyzed systematically. The results show that the microhardness of the composite coating (701.88HV0.5) is about two-fold of the substrate (350HV0.5). Due to the synergetic effect of the in-situ synthesized solid lubricants Ti2SC/TiS/NiS/TiO/TiO2/NiCr2O4/Cr2O3 and hard phases (W, Ti)C1-x/TiC/Cr7C3, both the wear resistant and friction reducing capabilities of the composite coating are better than that of the substrate. With the increase of temperature, the friction coefficient and wear rates of the composite coating and the substrate all exhibit decreasing trend, i.e., the friction coefficient of the composite coating and substrate are 0.32, 0.43 and wear rates are 1.80×10-4, 2.92×10-5mm/Nm at 800℃, respectively. The main wear mechanisms of substrate are mainly plastic deformation and delamination as well as oxidation wear, while the composite coating is predominated by the oxidation wear and slight adhesive wear at 800℃.

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    Influence of SiC nanoparticles on microstructure and corrosion behavior of microarc oxidation coatings formed on TC4 alloy
    Hai CHANG, Xue-gang GUO, Lei WEN, Ying JIN
    2019, 47 (3): 109-115.   DOI: 10.11868/j.issn.1001-4381.2018.000766
    Abstract ( 625 ( PDF (7786KB)( 396 Citation

    A microarc oxidation (MAO) coating was fabricated on the surface of TC4 alloy by adding SiC nano-particle into the base electrolyte. The influence of nanoparticles on the microstructure and corrosion behavior of MAO coatings was investigated. The results show that the introduction of SiC nanoparticles into the base electrolyte makes the coating thickness of MAO coating increased, from 9.2, 12.8, 12.4μm to 12.0, 14.9, 20.0μm, respectively, under the conditions of 550, 600V and 650V. The surface roughness of the coating (2.65, 3.34μm and 3.61μm) fabricated in SiC-containing solution increases with increasing the applied voltage. The introduction of SiC nanoparticles can effectively inhibit the microcracks in the coating, the coating thickness increase, and reduce the anodic current density, and thus the corrosion property of MAO coating increases. The OCP(open circuit potential) and corrosion potential increase by MAO coating.

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    Effect of alloy composition on morphology and volume fraction of quasi-crystalline of Mg-Zn-Y alloy
    Jiao-na YUAN, Jian-li WANG, Zhong YANG, Yong-chun GUO, Jian-ping LI
    2019, 47 (3): 116-122.   DOI: 10.11868/j.issn.1001-4381.2018.000587
    Abstract ( 667 ( PDF (11108KB)( 319 Citation

    Mg-Zn-Y alloys with a Zn/Y=6:1(atomic ratio) were prepared by steel mould casting method. The effect of alloy composition on phase constituents as well as the morphology, volume fraction of Mg3Zn6Y quasi-crystalline phase (quasi-crystalline Ⅰ-phase) in Mg-Zn-Y alloys was investigated by XRD, SEM, EDS, TEM and DSC. Results show that the phase constituents, the morphology, volume fraction and formation mechanism of Mg3Zn6Y quasi-crystalline Ⅰ-phase in the Mg-Zn-Y alloys are closely related to alloys' compositions. The formation reaction of quasi-crystalline Ⅰ-phase is transferred from fully peritectic reaction to the combination of peritectic and eutectic reactions, and to completely eutectic reaction with the decrease of Zn and Y content in the alloys. When the Y content is and more than 7%(atom fraction), the alloys are composed of (Mg, Zn)5Y, quasi-crystalline Ⅰ-phase, Mg2Zn3 and Mg7Zn3 phases and they are distributed in a layered form in the alloy, and the quasi-crystalline Ⅰ-phase takes the polygonal form by peritectic reaction during solidification. When the Y content is less than 7%, Mg phase precipitates in the alloys and their microstructure consists of (Mg, Zn)5Y, quasi-crystalline Ⅰ-phase, Mg7Zn3 and Mg phases. When the Y content is between 5% and 7%, the quasi-crystalline Ⅰ-phase is precipitated by peritectic and eutectic reaction, and eutectic reaction, which dominates the precipitation of quasi-crystalline Ⅰ-phase. When the Y content is and less than 4%, the quasi-crystalline Ⅰ-phase forms totally a (Mg+Ⅰ-phase) lamellar eutectic microstructure by eutectic reaction. The volume fraction of quasi-crystalline Ⅰ-phase is all greater than 27%, and in Mg30Zn60Y10 alloy is the maximum (about 77%) among the studied alloys.

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    Effect of trace germanium on microstructure and quenching sensitivity of 7056 aluminum alloy
    Wei LI, Kang-hua CHEN, Hui-bin JIAO, Liang ZHOU, Zhen YANG, Song-yi CHEN
    2019, 47 (3): 123-130.   DOI: 10.11868/j.issn.1001-4381.2018.000624
    Abstract ( 648 ( PDF (8896KB)( 317 Citation

    The effect of trace Ge on the microstructure and quenching sensitivity of 7056 aluminum alloy was studied by mechanical tensile and end quenching experiments, combined with some analysis methods such as metallographic observation, hardness test, conductivity test, scanning electron microscopy (SEM) and transmission electron microscopy (TEM).The results show that the trace element can refine the alloy grain sizes, the grain size is reduced from 137μm to 114μm; the addition of trace Ge formes coarse Mg2 Ge phase on the grain boundary and inhibits the formation of the T phase.In addition, compared with the Ge-free alloy, the width of the precipitation free zone of the Ge-bearing alloy becomes narrow, and is decreased from 190nm to 90nm, and the size of the precipitated phase at the grain boundary is reduced.The trace addition of Ge could reduce the quench sensitivity of alloy, increased the quenching depth of the alloy about 25%, which may be caused by the addition of Ge which changes the number and size of η equilibrium phase during slow cooling; the addition of Ge reduces the free vacancy concentration in the alloy, non-uniform nucleation and growth of the η equilibrium phase at the defect are suppressed, which increases the number of strengthening η' precipitates after aging.Thus the drop in the strength is decreased during slow quenching, which increases the hardenability of the alloy.

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    Crack initiation and early propagation behavior of AlSi10Mg(Cu) cast alloy under thermal fatigue
    Hang ZHOU, Zheng ZHANG
    2019, 47 (3): 131-138.   DOI: 10.11868/j.issn.1001-4381.2017.000231
    Abstract ( 761 ( PDF (14868KB)( 356 Citation

    The damage evolution under thermal fatigue loading for AlSi10Mg(Cu) cast alloy on the crack initiation and early propagation stage, mainly focusing on the influence of silicon particles on the thermal fatigue crack behaviour. The results show that, thermal fatigue crack origins from the failure interfaces between debonded silicon particles and matrix, that is because of the difference in thermal expansion coefficient between silicon particles and aluminum matrix, thus leading to the misfit of thermal strain, finally caused cyclic stress on the interfaces with fatigue failure. The propagation of thermal fatigue crack related to the growth on both length and width direction, ductile dendrite hinders the propagation of fatigue crack. The result of simulation analysis about the stress distribution around silicon particles during thermal fatigue is given to help discuss the experiment results.

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    Aging embrittlement at high temperature of 9Cr3W3Co steel and its improvement method
    Long-teng MA, Zheng-dong LIU, Yin BAI
    2019, 47 (3): 139-146.   DOI: 10.11868/j.issn.1001-4381.2016.001344
    Abstract ( 655 ( PDF (10237KB)( 348 Citation

    The main factor that results in aging embrittlement of 9Cr3W3Co steel was investigated through microstructure observation using scanning electron microscopy (SEM). The amount of each precipitates under equilibrium state in 9Cr3W3Co steel with different W content (W content is 2.36%, 2.63%, 2.96% and 3.11%, mass fraction) was calculated using Thermo-Calc software. The microstructure evolution during aging was studied by transmission electron microscopy (TEM), small angle X-ray scattering (SAXS) and phase analysis method. The results show that the rapid drop of impact toughness after aging for 100h is caused by the formation of Laves phase. The mass fraction of Laves phase at equilibrium state is mainly determined by the concentration of tungsten. The steel with lower tungsten content exhibits higher impact toughness after aging for 8000h, meanwhile with the smallest size and the lowest coarsening rate of Laves phase. Thus, the aging embrittlement of 9Cr3W3Co steel can be successfully suppressed by the reduction of tungsten content.

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    First principles on bcc and fcc phases structure of Fe52T2 (T=Cr, Mn, Co, Ni) alloys
    Xue DONG, Shuang MA, Xiao-xia WU, Ri-su NA
    2019, 47 (3): 147-153.   DOI: 10.11868/j.issn.1001-4381.2017.000002
    Abstract ( 903 ( PDF (2560KB)( 326 Citation

    The lattice parameter, local magnetic moment and the relative stability of ferromagnetic bcc and antiferromagnetic fcc phases structure of Fe52T2(T=Cr, Mn, Co, Ni) alloys were studied by first principles method based on density functional theory. The results show that the dependence of lattice parameters and bulk modulus on the d shell electron number of dopant elements cannot be simply explained by the d band filling image. This fact suggests that there is a strong magneto-structural coupling effect in FeT alloys. For FeT alloys, the ferromagnetic bcc phase is more stable compared with the fcc phase. The antiferromagnetic phase is tetragonal with c/a ratio about 1.07, and this phase structure can be a metastable state. The change of lattice structure leads to redistribution of electrons, and thus results in different magnetic order and local magnetic moment.

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    Microstructure and mechanical properties of Cu/Al2O3 composite prepared by metal injection molding after mechanical alloying
    Yi-qiang HE, Hu-lin XU, Chen-chen QIAN, Li-chao FENG, Bin QIAO, Feng SHANG, Hua-qiang LI
    2019, 47 (3): 154-161.   DOI: 10.11868/j.issn.1001-4381.2016.001322
    Abstract ( 632 ( PDF (11390KB)( 340 Citation

    10%(volume fraction)Cu/Al2O3 composite was prepared by the process of mechanical alloying and powder injection molding, the effect of alloying time and sintering temperature on microstructure and properties of the composite was investigated, and toughening mechanism of the composite was analyzed. The results show that 10%Cu/Al2O3 composite with good bending strength and fracture toughness can be prepared by the process of mechanical alloying for 10h, degreasing and then sintering at 1550℃. Bending strength and fracture toughness of the composite prepared by this process are up to 532MPa and 4.97MPa·m1/2 respectively. Due to weak diffusion of solid atoms for the composite being sintered below 1550℃, and mobility of particle boundaries being higher than pore escaping rate for the composite being sintered above 1550℃, porosity of the composite increases, and which results in strength and fracture toughness decreasing. Extending alloying time brings grain refinement and strong bonding between Cu and Al2O3 which is beneficial to elevate strength and hardness of the composite, while it is harmful to fracture toughness of the composite. Cu powders dispersing in the Al2O3 matrix protect the Al2O3 grains from coarsening during sintering process. And increasing in toughness of ceramic composite can be attributed to crack bridging and crack deflection when the cracks encounter the ductile Cu.

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