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      20 January 2017, Volume 45 Issue 1 Previous Issue    Next Issue
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    ZrC Ceramics Prepared by Self-propagating High-temperature Synthesis/Single Action Pressing
    Yong CHENG, Xun-jia SU, Gen-liang HOU, Zi-liang SHI, Chang-rong ZHONG, Ya-kun XING
    2017, 45 (1): 1-6.   DOI: 10.11868/j.issn.1001-4381.2015.000125
    Abstract ( 969 ( PDF (973KB)( 129 Citation

    ZrC ceramics were prepared by mechanical axial compression of self-propagating high-temperature synthesis/single action pressing (SHS/SAP).The effects of pressure on microstructure and densification of the products, as well as the relationship between displacement/variation of the load curve and SHS reaction, were studied.The structure and properties of the products were investigated by XRD and SEM.In addition, the density was measured by the drain away liquid method.Meanwhile, universal testing machine was used to record the displacement and load curve alternations.The results indicate that products are mainly composed of ZrC phase, the process of exhaust are accelerated as the increasing of pressure as well, leading to the smaller size of porosity and crystal particles.Density manifested as an increasing pattern by the elevated pressure with no longer change at 80 MPa.Due to the strong attenuation of pressure at the peak of temperature, the density of the production is only 65.7% in 120 MPa.The end point of the SHS reaction and the plastic time of the products can be monitored by displacement and load curve.The results provide evidence for the application of self-propagating high-temperature synthesis/pseudo-hot isostatic pressing to further improve the density of ceramics.

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    Effect of Prior Deformation on Welding Microstructure of Steel 304L
    Luo-fei WU, Qiang CHENG, Zhu-guo LI
    2017, 45 (1): 7-13.   DOI: 10.11868/j.issn.1001-4381.2015.000051
    Abstract ( 721 ( PDF (1336KB)( 112 Citation

    This subject was raised by an automotive company.Based on the welding design on the curved surface, the effect of prior deformation on the weld structure was studied.Metal active-gas welding was used on the T-joint and pre-deformed plates of austenitic stainless steel 304L to find the proper welding parameters and observe the effect of prior deformation on the microstructure.The proper parameters acquired are:the speed of the torch is 4 mm/s, the speed of delivery of welding wire is 2.5 m/min and the voltage is 17 V.In the T-joint and pre-deformed joint, the weld toes are in the zone with strain of 0% and 30%.In the pre-deformed welding specimen, it was observed that the fusion zone and partially melted zone are narrowed, carbide precipitation and ferrites are found less.In all, the microstructure in the pre-deformed weld joints on 304L is more uniform.

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    Microstructure Evolution of New Al-Zn-Mg-Cu Alloy During Hot Deformation
    Kun ZHANG, Jin-xin ZANG, Jun-zhou CHEN, Lin-na YI, Ji-gang RU, Wei KANG
    2017, 45 (1): 14-19.   DOI: 10.11868/j.issn.1001-4381.2016.000759
    Abstract ( 798 ( PDF (1163KB)( 168 Citation

    Microstructure evolution during hot deformation of a new Al-Zn-Mg-Cu alloy was investigated by Gleeble-1500D thermal-mechanical simulator at 300-450℃ and strain rate of 0.001-10 s-1.The microstructure features at different hot deformation conditions were analyzed with optical microscope (OM) and transmission electron microscope (TEM).The results show that the dislocation density decreases and the subgrain sizes increase with the increase of deformation temperature and the decrease of the strain rate; the main softening mechanism of the alloy is dynamic recovery and dynamic recrystallization.Only dynamic recovery occurs when the temperature is 300-400℃.Dynamic recrystallization occurs when the strain rate is 0.001-10 s-1 at 450℃.The nucleation mechanism is grain boundary bowing, subgrain growing and subgrain incorporation during dynamic recrystallization.

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    Effect of Dynamic Composite Refinement and Modification on Microstructure of A356 Aluminum Alloy
    Zheng-jun WANG, Nai-chao SI, Jun WANG, Ran DING, Hao WAN, Guang-lei LIU
    2017, 45 (1): 20-26.   DOI: 10.11868/j.issn.1001-4381.2015.000077
    Abstract ( 853 ( PDF (944KB)( 247 Citation

    To make up for the inadequacy of Sr modification, Al-5Ti-1B-1RE master alloy refiner was prepared, then were used together with Al-10Sr master alloy for dynamic composite refinement and modification of A356 alloy.The A356 alloy microstructure of modification was studied and compared with the theoretical calculating results.The results show that the melt is fiercely stirred and vibrated by the JJ-1 laboratory electric stirrer; the refining effect of α-Al phase is excellent; the coarse and needle-like eutectic Si phase transforms into tiny, widely dispersed spherical particles and well-distributed at the grain boundaries.And mechanical property of the A356 alloy increases obviously.The grain size control study results are consistent with Johnson-Mehl equation theory.At the same time, the contents of gases of the A356 alloy are significantly reduced, which can not be achieved by Sr alone.Quantitative calculating results of degassing mechanism are consistent with the approximate calculating equations of thermodynamics and Stokes Law.

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    Microstructure and Mechanical Properties of Laser Melting Deposited GH4169 Superalloy
    Bo-rui DU, Xue-jun ZHANG, Shao-qing GUO, Neng LI, Bing-bing SUN, Si-yi TANG
    2017, 45 (1): 27-32.   DOI: 10.11868/j.issn.1001-4381.2014.001258
    Abstract ( 892 ( PDF (986KB)( 191 Citation

    The block samples of a Ni-based superalloy named GH4169 were prepared by laser melting deposited method using the corresponding GH4169 alloy powders, and then were heat treated with solution treatment followed by double aging.The microstructure and element segregation analysis of both as-deposited and heat treated samples were studied by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS).The microhardness as well as tensile properties at room and elevated temperatures were tested.The results indicate that the microstructure of as-deposited sample mainly consists of columnar dendritic crystals that grow along with different directions.Grains are refined after solution and aging heat treatment, but remain dendritic crystals substructure inside.Compared with the as-deposited sample, the microhardness and tensile strength of the heat treated sample increase substantially, but the plasticity somewhat decreases.Nonetheless the tensile properties are superior to the standard values of forgings.The fracture surface exhibits ductile transcrystalline fracture mode.

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    Dielectric Properties of Ferrite/Silicon Carbide/Graphite Three-layer Composite Coating Materials
    Xiao-ming ZHAO, Yuan-jun LIU
    2017, 45 (1): 33-37.   DOI: 10.11868/j.issn.1001-4381.2015.000775
    Abstract ( 1129 ( PDF (852KB)( 176 Citation

    The flexible knitted polyester fabric was used as a base material and a three-layer composite coating was applied to the structure material by using ferrite, silicon carbide, and graphite absorbing materials, and the composites were prepared with different coating thickness.The influences of the thickness of the bottom layer, the middle layer, and the surface layer coating on permittivity's the real part, the imaginary part and loss tangent were discussed.The results show that the dielectric properties of the composite material are sound at low frequencies.The thickness of the coating has a clear influence on the permittivity's real part, the imaginary part and the loss tangent of the composite material.When the thickness of the bottom coating layer is 0.5 mm, the thickness of the middle coating layer is 0.3 mm, and the thickness of the surface coating layer is 0.3 mm, the permittivity's real part, imaginary part, and loss tangent of the ferrite/silicon carbide/graphite coating composite material reaches the maximum value.

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    Preparation and Properties of Superamphiphobic Wear-resistance PPS-based Coating
    Huai-yuan WANG, En-qun WANG, Yang MENG, Yan-ji ZHU
    2017, 45 (1): 38-42.   DOI: 10.11868/j.issn.1001-4381.2015.000101
    Abstract ( 1189 ( PDF (870KB)( 231 Citation

    Superamphiphobic wear-resistance PPS-based coatings were prepared by a simple spraying method with a pore-forming reagent of NH4HCO3 and nano-filler of carbon nanotubes (CNTs).The surface morphology and the hydrophobicity, oleophobicity of the coating were analyzed by scanning electron microscope (SEM) and contact angle meter.The wear-resistance of the coating was verified by sanding method with given load.The results indicate that a rough surface is obtained after pore-forming, and the porous structures in combination with the CNTs construct the special micro/nano-scale network structures.When the mass fraction of NH4HCO3 is 5%, the contact angles of the coating for water, glycerine and ethylene glycol are 162°, 158° and 152°, showing superamphiphobic property.After polished 10000 times by abrasive paper, the coating shows slight friction marks and remains high hydrophobicity, exhibiting excellent wear-resistance.

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    Hot-corrosion Behavior of HR3C Pre-coated Alkali Metal Sulphate in SO2 Atmosphere
    Ping LI, Peng QIN, Jie ZHAO, Ting-ju LI, Sheng-jiao PANG
    2017, 45 (1): 43-51.   DOI: 10.11868/j.issn.1001-4381.2015.000295
    Abstract ( 707 ( PDF (1203KB)( 112 Citation

    The corrosion behaviors of HR3C pre-coated alkali metal sulphate in SO2 atmosphere at different temperatures were investigated by means of XRD, SEM (EDS) and EMPA in order to discuss the corrosion resistance mechanism to SO2 of HR3C.The results show that the corrosion kinetic curves follow parabolic law.The corrosion products are mainly composed of (Fe, Cr) oxides, minor compound oxides with spinel structure as well as (Fe, Ni) sulfides.The increment in SO2 content increases significantly the oxide films in thickness, and deteriorates the adhesion to the oxide scale and matrix.In addition, the porosities in the corrosion affected zone (the interface between the oxide films and the matrix) increase and a CrS belt exits in the interface between the oxide layer and the corrosion affected zone.The analysis shows that the corrosion of HR3C in SO2 environment is resulted from the oxidation, sulfidation of the alloy, moreover, the sulfation of metallic oxides and the formation of ternary composed alkali metal sulfate as well as the dissolution of Fe in melted salt also contribute to the corrosion.

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    Effect of Nano-TiC Particles on Microstructure and Properties of Ni-TiC Composite Coatings
    Hong-xing WANG, Xiang-yang MAO, Tong SHEN, Yue ZHANG
    2017, 45 (1): 52-57.   DOI: 10.11868/j.issn.1001-4381.2014.001571
    Abstract ( 817 ( PDF (964KB)( 100 Citation

    Ni based composite coatings containing micro-and nano-TiC particles were prepared by dipulse electrodepositing in Watt's nickel solution.The effect of nano-TiC content in the solution on the micro morphology, microstructure, hardness and wear resistance of composite coatings was investigated.The results show that the agglomeration of composite coatings of Ni-TiC appears and the density decreases by adding nano-TiC particles in electrolyte, the microstructure of coatings consists of Ni and TiC phase; the hardness of composite coatings firstly increases and then decreases with increasing the content of nano-TiC in bath; however, the friction coefficient of coatings firstly decreases and then increases, the maximum value of microhardness of coating with 445HV is achieved when containing 6.0g/L nano-TiC in bath, at the same time, the smaller friction coefficient of coating is about 0.22.The wear mechanism is mainly abrasive wear.Coatings under the oxidation condition at 900℃ for 100h show the best oxidation resistance which the mass gain with 6.828mg/cm2 is 1/2 of that of micro-TiC composite coating.

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    Preparation and Performance Analysis of Na2SO4·10H2O/EG Composite Phase-change Materials
    Cong-bin LENG, Xu JI, Xi LUO, Ming LI, Qiong-fen YU, Yong-feng XU
    2017, 45 (1): 58-64.   DOI: 10.11868/j.issn.1001-4381.2015.000073
    Abstract ( 863 ( PDF (854KB)( 283 Citation

    Sodium sulfate decahydrate/expanded graphite composite phase-change material (Na2SO4·10H2O/EG) was prepared by vacuum adsorption method.The thermal properties of Na2SO4·10H2O/EG, such as melting-solidification, phase separation, supercooling and latent heat were tested and analyzed.The results show that with the addition of 2%(mass fraction) borax and 8% EG, the composite phase-change materials Na2SO4·10H2O/EG obtain ideal properties.The phase separation is eliminated, the supercooling degree of Na2SO4·10H2O is reduced from 13.6℃ to below 0.6℃, the latent heat and the energy storage density of the phase-change materials reach 225.77kJ·kg-1 and 218.09MJ·m-3 respectively.The thermal conductivity is also greatly improved.Compared with Na2SO4·10H2O with the addition of the nucleating agent borax only, the time for heat storage is shortened by 52.6%, and the time for heat release is shortened by 55.1%.Even after 500 times of rapid heating and cooling cycles, the performance of Na2SO4·10H2O/EG does not deteriorate.The novel composite phase-change material has better storage/exothermic properties.

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    Effect of Laser Heat Treatment on Microstructures of 1Cr5Mo Steel Welded Joint
    Wei GUO, De-jun KONG, Wen-chang WANG
    2017, 45 (1): 65-71.   DOI: 10.11868/j.issn.1001-4381.2015.000237
    Abstract ( 791 ( PDF (1266KB)( 124 Citation

    The surface of 1Cr5Mo heat-resistant steel welded joint was treated with CO2 laser, the microstructure and grain size grades of welded joints before and after laser heat treatment (LHT) were analyzed with 4XC type optical microscope (OM), and the distribution of residual stress and retained austenite content in the surface of the welded joints were measured with X-ray diffraction (XRD) stress tester.The results show that the grains of 1Cr5Mo steel welded joints are refined by LHT, and the microstructure uniformity improves significantly, the grain levels of welded zone, fusion zone, overheated zone and normalized zone increase from level 9, level 9.8, level 8 and level 10.7 to level 10, level 10.2, level 8.5 and level 11 respectively, the mechanical weak areas reduce from overheated zone, welded zone and fusion zone to the overheated zone.The tensile residual stress in the welded joint surface is eliminated by LHT and a layer of compressive residual stress with thickness of about 0.28mm is formed.The residual austenite content in the welded joint surface increases after LHT, of which the distribution is more uniform and conducive to the improvement of mechanical properties.

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    Bulging Behavior of Thin-walled Welded Low Carbon Steel Tubes
    Wen-cai XIE, Shi-jian YUAN
    2017, 45 (1): 72-77.   DOI: 10.11868/j.issn.1001-4381.2015.000312
    Abstract ( 487 ( PDF (1015KB)( 119 Citation

    In order to investigate the deformation behaviour of welded tubes during hydraulic bulging process, the hydraulic bulging tests of thin-walled welded low carbon steel tubes (STKM11A) were conducted on the tube hydroformability testing unit.The thickness distribution, profiles of bulging area and the strain distribution were all obtained.Results show that the thickness reduction of weld zone is just 2.4%-5.5% while its effective strain is just 0.05-0.10, which is very small and negligible compared with the parent material and means that just the geometric position of weld zone is changed with the continuous bulging.The thinnest points are located on the both sides of weld seam symmetrically and the angle between the thinnest point and weld seam is about 30°, at which the necking has been occurred.When the length of bulging area increases, the fracture pressure, the thickness reduction and the ultimate expansion ratio all decrease, and the profile of the bulging area gradually steps away from the elliptical model which is powerless for the ratio of length to diameter up to 2.0.Moreover, the strain state of the tube is transformed from biaxial tension to plane strain state with the increasing length of bulging area, on the basis of this the forming limit diagram of welded STKM11A steel tubes can be established.

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    Prediction on Austenite Grain Growth in High Carbon Steel
    Han MA, Shu-lun LIAO
    2017, 45 (1): 78-84.   DOI: 10.11868/j.issn.1001-4381.2014.001547
    Abstract ( 865 ( PDF (987KB)( 168 Citation

    The austenite grain growth behavior of Ti-bearing and Ti-free steel was investigated using confocal laser scanning microscope (CLSM) and transmission electron microscope (TEM).Samples were held for 60min at 1123-1473K and then austenite grain sizes for different holding time at a series of temperatures were measured.The results show that austenite grain size of both steels increases with the increase of temperature.Besides, the austenite grain size of both steels grows with the holding time, which meets parabolic equation.The second phase particle was observed.The equation of Ostwald ripening was introduced to calculate the size of particle, and the volume fraction equation of second phase particle was applied to calculate the volume fraction of particle.Meanwhile, the modified Gladman model was adopted to predict austenite grain growth.The predicted results agree well with the measured results.

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    Effect of WCp Content on Fatigue Crack Growth Behavior of Powder Metallurgy Cu/WCp Composites
    Yu-bo ZHANG, Rong-xin GUO, Hai-ting XIA, Feng YAN, Zhi-wei LIN
    2017, 45 (1): 85-92.   DOI: 10.11868/j.issn.1001-4381.2015.001530
    Abstract ( 637 ( PDF (1365KB)( 143 Citation

    The high voltage electric contact Cu/WCp particles reinforced composite material was prepared by powder metallurgy hot pressing sintering method.The effect of WCp particle contents (15% and 3%, volume fraction, the same as below) on the fatigue crack growth behavior of Cu/WCp composite was studied and the fracture surface was analyzed by SEM.The observation of the fatigue crack initiation and the influence mechanism of particle on fatigue crack growth was carried out by in-situ scanning electron microscopy (SEM).Results show that the fatigue crack growth rate of Cu/WCp/15p composites is faster than that of Cu/WCp/3p composites at the same stress intensity factor range (ΔK); with the increase of WCp content, the threshold stress intensity factor range ΔKth is not enhanced because the interface of the particles and the matrix are weak.From the results of in-situ SEM observation fatigue crack growth can be seen that the crack source is formed due to the particle debonding during fatigue process, different debonding microcracks connect and grow to form main cracks is the fatigue damage mode of Cu/WCp particle reinforced composites.When the main crack tips encounter WCp particles, cracks propagate forward along the particle interface.The fractographies show that the fracture mode of the composites is from particle debonding-transgranular fracture in matrix at the low content 3% to particle debonding-tear in matrix at the high content 15%.

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    Deformation and Damage Mechanism of a 4.5% Re-containing Nickel-based Single Crystal Superalloy During Creep at 980℃
    De-long SHU, Su-gui TIAN, Shuang LIANG, Bao-shuai ZHANG
    2017, 45 (1): 93-100.   DOI: 10.11868/j.issn.1001-4381.2016.000599
    Abstract ( 729 ( PDF (1040KB)( 145 Citation

    By means of creep property measurements and microstructure observations, an investigation has been made into creep behaviors, deformation and damage mechanism of a 4.5%(mass fraction, the same below) Re-containing, nickel-based single crystal superalloy at 980℃.Results show that, under the condition of 980℃/300MPa, the creep life of 4.5% Re alloy is 169h.In the initial stage of creep, the cubical γ'phase in alloy is transformed into the N-type rafted structure perpendicular to the stress axis.During the steady stage creep, the deformation mechanism of the alloy is dislocations slipping in γ matrix and climbing over the rafted γ'phase.In the last stage of creep, the deformation mechanism of alloy is dislocations slipping in γ matrix and shearing into the rafted γ'phase.On the one hand, the γ matrix channels with narrower feature increases the resistance of dislocations slipping; on the other hand, the super-dislocations shearing into the rafted γ'phase may cross-slip from{111}plane to{100}plane to form the dislocation configuration of K-W locks, which may restrain the slipping and cross-slipping of dislocations to improve the creep resistance of alloy.Moreover, the alternate activation of the primary/secondary slipping dislocations results in the twisting of the rafted γ'phase to promote the initiation of the cracks on the γ'/γ interfaces, and as the creep goes on, the cracks propagate along the direction perpendicular to the direction of stress axis, up to creep fracture, which is thought to be the fracture mechanism of the alloy during creep.

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    Progress in Research on Bonding Interface Between Thermal Spraying Coating and Substrate
    Jian LIU, Fan-jun MENG, Feng-liang YIN, Yong-xiong CHEN, Xiu-bing LIANG
    2017, 45 (1): 101-110.   DOI: 10.11868/j.issn.1001-4381.2014.001230
    Abstract ( 845 ( PDF (915KB)( 324 Citation

    In the process of thermal spraying remanufacturing, a heterogenerous bonding interface always exists between the coating and matrix due to the materials reason.And the formation and existence of the bonding interface has a significant influence on the coating performance.In this paper, research progress on bonding interface between thermal spraying coating and substrate was summarized, mainly focused on the forming mechanism of bonding interface and its effect on coating performance.The problems on the research of bonding interface between the thermal spraying coating and substrate were analyzed, and aiming at these problems, some suggestions were put forward, such as adopting new technology and approaches to investigate the growing process of the bonding interface in order to reveal its forming mechanism, exploiting new characterization method to realize quantitative characterization of bonding interface morphology and structure so as to build the quantitative relationship between bonding interface and coating properties, and etc. and to lay foundation for the implementation on design and control of the coating properties and life prediction.

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    {332}〈113〉 Deformation Twinning in Metastable β-type Titanium Alloys
    Bin CHEN, Wei SUN, Jie ZHAO, Chang-qing HU
    2017, 45 (1): 111-119.   DOI: 10.11868/j.issn.1001-4381.2015.000449
    Abstract ( 603 ( PDF (1163KB)( 162 Citation

    {332} < 113> deformation twinning is a unique deformation mode which can have some special features and a strong influence on the mechanical properties for metastable β-type titanium alloys.{332} < 113> deformation twinning has already got more and more attention.The research situation and observed characteristics for the {332} < 113> deformation twinning are summarized in this paper.Some typical models for the {332} < 113> twinning are reviewed, and their assumptions and remaining problems are presented so as to provide useful information for understanding and revealing the deformation mechanism of {332} < 113> deformation twinning.

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    Research Progress on Laser Cladding Amorphous Coatings on Metallic Substrates
    Ming-hui CHEN, Hong-mei ZHU, Xin-lin WANG
    2017, 45 (1): 120-128.   DOI: 10.11868/j.issn.1001-4381.2015.000459
    Abstract ( 981 ( PDF (697KB)( 411 Citation

    The microstructure and property of amorphous alloy as well as the limitations of the traditional manufacturing methods for the bulk amorphous alloy were briefly introduced in this paper.Combined with characteristics of the laser cladding technique, the research status of the laser cladding Fe-based, Zr-based, Ni-based, Cu-based and Al-based amorphous coatings on the metal substrates were mainly summarized.The effects of factors such as laser processing parameter, micro-alloying element type and content and reinforcing phase on the laser cladding amorphous coatings were also involved.Finally, the main problems and the future research directions of the composition design and control of the laser-cladded amorphous coating, the design and optimization of the laser cladding process, and the basic theory of the laser cladding amorphous coatings were also put forward finally.

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