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      20 October 2014, Volume 0 Issue 10 Previous Issue    Next Issue
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    Microstructure and Tensile Properties of AZ91D Magnesium Alloy by Forced Convection Rheo-diecasting Process
    ZHOU Bing, KANG Yong-lin, QI Ming-fan, ZHANG Huan-huan, ZHU Guo-ming, WU Zheng-yang
    2014, 0 (10): 1-5.   DOI: 10.11868/j.issn.1001-4381.2014.10.001
    Abstract ( 935 ( PDF (2413KB)( 197 Citation
    The microstructure characteristics of AZ91D magnesium alloy connectors were investigated in traditional die-casting and rheo-diecasting process. The formation and solidification behavior of semi-solid slurry were analyzed. The tensile properties of rheo-diecasting tensile samples were tested. The results indicate that the forced convection rheo-diecasting process is able to obtain semi-solid microstructure with fine and near spherical grain. And the process can significantly improve porosity defects existed in traditional die castings and increase density. Compared with conventional die castings,the tensile strength and elongation of rheo-diecasting tensile samples have been significantly improved. T6 heat treatment further strengthens the property of rheo-diecasting tensile samples with the tensile strength of 286 MPa and elongation of 6.1%
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    Glass Forming Ability and Magnetic Properties of Fe-Nd-B-Zr Bulk Metallic Glasses
    LIU Fan-mao, ZHANG Hui-yan, ZHANG Tao
    2014, 0 (10): 6-10.   DOI: 10.11868/j.issn.1001-4381.2014.10.002
    Abstract ( 888 ( PDF (1426KB)( 285 Citation
    Permanent magnets with Fe-Nd-B bulk metallic glasses as precursors was fabricated. Trace zirconium was added into Fe70Nd10B20 ternary alloy and its adjacent composition. The samples were prepared by spin quenching and copper mold casting,and the glass forming ability was characterized by XRD and DSC. Then the Fe70Nd9B20Zr1 bulk metallic glasses were crystallized by annealing treatment. The crystallization phases were analyzed by XRD and the magnetic properties in various crystallization stages were characterized by VSM. The results show that the glass forming ability of the alloys is enhanced,and Fe-Nd-B-Zr bulk metallic glasses with critical diameter of 2 mm are obtained in alloys containing 1% atom fraction Zr. The optimum hard magnetic properties of Fe70Nd9B20Zr1 bulk metallic glasses can be achieved after annealing at 946 K for 600 s.The remanence (Br),coercive field (iHc) and maximum energy product (BH)max are 0.54 T,348 kA/m and 24.1 kJ/m3,respectively.This alloy system can be applied to directly synthesize nanocomposite permanent magnets by the process of casting and subsequent crystallization.
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    Microstructure and Mechanical Properties of Linear Friction Welded P/M Superalloy FGH96
    MA Tie-jun, WANG Wei, LI Wen-ya, ZHANG Yong
    2014, 0 (10): 11-15.   DOI: 10.11868/j.issn.1001-4381.2014.10.003
    Abstract ( 889 ( PDF (1755KB)( 249 Citation
    Linear friction welding (LFW) of powder metallurgy superalloy FGH96 was carried out by using homemade LFW machine (XMH-160). The microstructure was analyzed and tensile property and microhardness of joints were examined.The results show that the joint could be divided into three zones: weld zone,thermomechanically affected zone (TMAZ) and base metal. The weld zone presents typical fine grains,while the coarse and fine grains co-exist in the TMAZ. The tensile strength of joints is comparable to the base metal,but the ductility of joints is worse than that of the base metal. The microhardness presents a high-low-high tendency across the weld line with the lowest value in the middle of TMAZ. The mechanical properties of joints in different zones are associated with the content and distribution of strengthening phases and the lattice distortion in addition the grain size. Therefore,for LFW FGH96 superalloy,the optimization of process parameters and post-weld heat treatment are necessary to improve the joint properties.
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    Vacuum Brazing of SiO2f/SiO2 and C/C Composite Using Ag-Cu-Ti Filler Alloy
    WU Shi-biao, XIONG Hua-ping, CHEN Bo, CHENG Yao-yong
    2014, 0 (10): 16-20.   DOI: 10.11868/j.issn.1001-4381.2014.10.004
    Abstract ( 850 ( PDF (1731KB)( 309 Citation
    SiO2f/SiO2 composite was joined to C/C composite using Ag-Cu-Ti active brazing foils at brazing temperature of 880℃ for 10min and 60min,respectively. The microstructure of joint was analyzed by electron probe micro-analyzer(EPMA),X-ray energy dispersive spectrometer(XEDS) and X-ray diffraction(XRD). Meanwhile,the shear strength of joints was tested at room temperature. The results show that sound joints are achieved and two thin diffusion reaction layers have been formed close to the base materials. The brazing seam matrix is composed of homogeneous eutectic alloy. The typical interface structure of joint brazed at 880℃ for 10min can be described as the following sequence: SiO2f/SiO2→Ti4O7→Ti5Si4+Cu(s,s)+Ag-Cu eutectic alloy→TiC→C/C.The microstructure of the joints brazed at 880℃ for 60min is similar to the former except the absence of Cu(s,s). Furthermore,the reaction layers of joints brazed for 60min are much thicker than those brazed for 10min. The joints brazed at 880℃ for 60min show an average shear strength of 16.6MPa.
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    Adhesive of Bisphthalonitrile Resin
    LI Hong-feng, ZHOU Heng, WANG De-zhi, QU Chun-yan, ZHAO Tong, GU Ji-you
    2014, 0 (10): 21-26.   DOI: 10.11868/j.issn.1001-4381.2014.10.005
    Abstract ( 937 ( PDF (1489KB)( 417 Citation
    A kind of high-temperature resistant adhesive of bisphthalonitrile resin was developed by using self-synthesised bisphthalonitrile resin (BPh),and PAI as toughening agent and DP/BMI as promoter. The curing behaviors of the adhesive were analyzed by DSC and FTIR. The thermal properties of the adhesive were evaluated by DMA and TGA,and the bonding strength of the adhesive was studied by material test machine. The results show that DP/BMI resin can promote curing reaction of the BPh resin adhesive,with the curing temperature of 260℃. BPh resin adhesive is effectively toughened by PAI with the drum peel strength of adhesive reaching 21.20N·mm/mm. BPh resin adhesive is qualified for its good heat resistance. The shear strength is 6.38MPa at 400℃,and the glass transition temperature is 329.6℃.The shear strength retention of the adhesive is above 80% after high-temperature aging.The shear strength retention is above 95% after heat-moisture aging.
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    Effect of Roll Convexity and Stress Triaxiality on Rolling Damage of 93 Tungsten Alloy Sheet
    WANG Jin, ZHAO Guo-qun, WANG Guang-chun, YUAN Jun
    2014, 0 (10): 27-33.   DOI: 10.11868/j.issn.1001-4381.2014.10.006
    Abstract ( 798 ( PDF (3681KB)( 214 Citation
    According to the numerical simulation model of the rolling process of powder sintered 93 tungsten alloy sheet and using the finite software DEFORM,the effect of roll convexity on head crack of the rolled sheet and the principal stress change in the crack point were analyzed.The results show that,with the increase of roll convexities,roll force and the rolled sheet width are on the rise,effective stress and effective strain change slightly,stress triaxiality and cracking tendency increase with the increasing of roll convexities absolute value,the selected range of roll convexities is-0.02-0.05mm.
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    Effect of Different Substrates on Microstructures and Mechanical Properties of Submicron Hypoeutectic White Cast Iron
    LA Pei-qing, LI Zheng-ning, HU Su-lei, LI Cui-ling, WEI Yu-peng, LU Xue-feng, WEI Fu-an
    2014, 0 (10): 34-39.   DOI: 10.11868/j.issn.1001-4381.2014.10.007
    Abstract ( 939 ( PDF (3372KB)( 223 Citation
    A white cast iron with submicron microstructure was prepared by an aluminothermic reaction casting on copper substrate and glass substrate. Microstructures and composition of the cast iron were investigated by optical microscope (OM),scanning electron microscope (SEM),X-ray diffraction (XRD),and electron probe micro-analyzer (EPMA). The hardness,compressive properties and tensile properties of the cast iron were also tested. The results show that the cast iron consists of pearlite and cementite phases. The average lamellar spacing of the pearlite phase on copper substrate and glass substrate is 220nm and 165nm respectively. Hardness of the cast iron is 564HV and 552HV,compressive strength is 2429MPa and 2224MPa,tensile strength is 391MPa and 383MPa,total elongation is 2% and 3% respectively.
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    Effect of C on TIG In-situ Alloying Welding of MGH956 Alloy
    REN Dan, LEI Yu-cheng, LIU Fa-qiang, LI Meng-gang
    2014, 0 (10): 40-46.   DOI: 10.11868/j.issn.1001-4381.2014.10.008
    Abstract ( 666 ( PDF (2640KB)( 177 Citation
    MGH956 alloy was welded by TIG in-situ alloying welding with homemade filler material. The in-situ alloying mechanism and behavior of C in the TIG welding process were mainly analyzed. The results show that the partial pressure effect of C to N can reduce the solubility of N in the welding pool. This eliminates the nitrogen porosity in welding process. TiC particles with the size of 50-100 nm form and distribute uniformly in the weld. Addition of moderate C to filler material can refine the grains size and improve the mechanical properties of weld. Thus the comprehensive properties of the weld are improved.
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    Effect of Cooling Regime on Precipitation of Ultra-fine Carbides of Ti-Mo Ferrite Matrix Microalloyed Steel
    SUN Chao-fan, CAI Qing-wu, CHEN Zhen-hua, CHEN Hong-zhen
    2014, 0 (10): 47-52.   DOI: 10.11868/j.issn.1001-4381.2014.10.009
    Abstract ( 912 ( PDF (2989KB)( 201 Citation
    The effect of different cooling rates on the precipitation of (Tix,Mo1-x)C particles was investigated by SEM,TEM and SAXS.The result show that a larger number of finer and more uniform precipitates can be obtained through inter-phase precipitation under the condition of a higher cooling rate during γ→α transformation,the size of these inter-phase precipitation particles are mostly 1-10nm.A further dispersion precipitation in ferrite matrix occured under a relatively slower cooling rate after γ→α transformation,these superfine dispersion precipitation particles helps to obtain a higher proportion of single nanometer-sized particles in microalloyed steel.
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    Friction and Wear Behaviors of VC Modified Layer Prepared by TD Process Under Different Loadings
    KONG De-jun, FU Gui-zhong, ZHOU Chao-zheng, WANG Wen-chang
    2014, 0 (10): 53-58.   DOI: 10.11868/j.issn.1001-4381.2014.10.010
    Abstract ( 845 ( PDF (2961KB)( 231 Citation
    The VC (vanadium carbide) modified layer was prepared on the cold working die steel of Cr12MoV with TD (thermal diffusion) process,the structures,morphologies,compositions and bonding strength of VC modified layer were characterized via SEM,EDS,XRD and ST (scratch test),respectively. The dry sliding friction test of GCr15 steel column against VC modified layer was processed,the wear performance and fretting wear behavior under the different loads were investigated. The results show that the VC modified layer is composed of VC phase,and the interface combine is a metallurgical bonding,whose average bonding strength is 51.2N by ST. The friction coefficient at stationary stage is increased with the load,the reasonable load can reduce friction coefficient and wear mass,and the fretting wear mechanism is abrasion wear. VC modified layer obviously increases the surface hardness and bearing capacity of Cr12MoV steel,and significantly improves its wear resistance,and the high hardness and bonding strength is the main mechanism of increasing wear resistance.
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    Segregation Behavior of Phosphorus for 2.25Cr-1Mo Steel at Subsequent Heat Treatment Process
    ZHANG Xi-liang, LIU Tao, CUI Guo-hua, ZHOU Chang-yu, LIU Zheng, ZHANG Wei
    2014, 0 (10): 59-64.   DOI: 10.11868/j.issn.1001-4381.2014.10.011
    Abstract ( 809 ( PDF (2000KB)( 228 Citation
    Grain boundary segregation behavior of phosphorus and de-embrittled treatment process for 2.25Cr-1Mo steel served 12 years were investigated in terms of the grain-boundary segregation and atomic diffusion theory. The segregation degree of phosphorus was tested by virtue of Auger electron spectrum. The results show that there is a critical embrittlement temperature corresponding to 2.25Cr-1Mo steel embrittled,and the critical embrittlement temperature will decrease as the embrittlement degree increases. Furthermore,the embrittlement can restore to its original state in a few hours at the temperature higher than the critical embrittlement temperature. That is,de-embrittlement rate is much faster than embrittlement rate for 2.25Cr-1Mo steel.
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    Effect of Mg on Microstructures and Abrasive Resistance of In-situ Synthesis TiC-Al2O3/Al Composites
    ZHANG Rui-ying, CHEN Su-juan, SHI Zhi-ming, ZHANG Lian-feng
    2014, 0 (10): 65-70.   DOI: 10.11868/j.issn.1001-4381.2014.10.012
    Abstract ( 840 ( PDF (2800KB)( 216 Citation
    TiC and Al2O3 particles reinforced aluminum matrix composite was synthesized from TiO2,C,Al and Mg powder by the in-situ method. The effects of Mg on the microstructure and abrasive resistance of TiC-Al2O3/Al composite were investigated using XRD,SEM and wear testing. The results show that Mg influences the reaction process and the second phase distribution. The abrasive resistance of the composites increases with increasing Mg content. When Mg content in green compacts reaches 1.0% (mass fraction),the reinforcement particles are the most uniform and the smallest. The average size of reinforcement particles is about 2μm. The abrasive resistance of composites is optimal and the abrasion loss is only 1/6 of the matrix. However,with the further increase of Mg content,the abrasion resistance of composites decreases inversely due to producing coarse needle-like Al3Ti.
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    Synthesis and Characterization of Palmitic Acid-hexadecanol/SiO2 Phase Change Energy Storage Materials by Solid-state Chemical Reaction at Low Temperature
    MA Feng, QIN Yan, LU Feng-yan, WANG Xiao-yan
    2014, 0 (10): 71-74.   DOI: 10.11868/j.issn.1001-4381.2014.10.013
    Abstract ( 916 ( PDF (1581KB)( 344 Citation
    Palmitic acid-hexadecanol/silicon dioxide (PA-HD/SiO2) phase change energy storage materials were prepared by low-temperature solid-state reaction using the eutectic mixture of palmitic acid and hexadecanol(PA-HD) as phase change component and sodium silicate as silicon source. The structure,morphology,and thermal performance of the composite were characterized by Fourier transform infrared spectrometer (FT-IR),environmental scanning electron microscopy (ESEM),differential scanning calorimetry (DSC),and the test of melting and solidification process. The results show that when the ratio of mass fraction between phase change component and sodium silicate is 2,the eutectic mixture of palmitic acid and hexadecanol are effectively imbedded into the net of silicon dioxide by low-temperature solid-state reaction. The latent heat and melting temperature of the composite are 102.35J·g-1 and 53.69℃,respectively,and the composite has good thermal conductivity. Furthermore,the phase transition temperature of the eutectic mixture is improved owing to the coating effect of silicon dioxide.
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    Evolution of Orientations and Their Influence on Precipitation During Hot Compression of Columnar-grained Electrical Steel
    SHAO Yuan-yuan, YANG Ping, MAO Wei-min
    2014, 0 (10): 75-81.   DOI: 10.11868/j.issn.1001-4381.2014.10.014
    Abstract ( 619 ( PDF (3079KB)( 192 Citation
    The evolution of initial orientations and their influence on precipitation of columnar-grained electrical steel after 50% hot compression deformation were investigated by electron backscatter diffraction technique and field emission scanning electron microscopy. The results indicate that the <100> orientated columnar grains remain still <100> after hot compression deformation,with only rotation around ND parallel to <100> direction,with heredity,and less precipitation. As the deviation angle between the long axis of columnar grain and the compression axis increases,the stability of initial grain orientation becomes poor,when the deviation angle is higher than 40°,the <111> oriented grains can be formed,during which higher defect density is formed due to the complex interaction of slip systems which facilitate the MnS precipitation. The MnS particles nucleate dominantly within hot compressed grains,particles can not be precipitated thoroughly either at high temperature or low reduction rate during hot compression,and in a subsequent recovery,the high deformation energy storage and defect density are prerequisite to promote further precipitation.
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    Characterizations of Tungsten Alloy Mechanical Property by Molecular Dynamic Simulations
    YU Chao, REN Hui-lan, NING Jian-guo
    2014, 0 (10): 82-89.   DOI: 10.11868/j.issn.1001-4381.2014.10.015
    Abstract ( 1013 ( PDF (4037KB)( 301 Citation
    Based on the combination of experiments and numerical simulations,the plastic properties of a 91%(mass fraction,the same below) refined particle tungsten alloy were investigated. The results show that refined tungsten alloy has a strain rate effect and the yield strength increases with the increase of strain rate. The temperature effect,size effect and crystal orientation effect appear obviously in the nano-tungsten alloy materials. By comparing the numerical results and the experimental results,the conclusion obtained is two methods are in good agreement.The accurateness of this molecular dynamic simulation and the reliability of the fitted power law formula at high strain rate state are proved.
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    Oxidation Behavior of Si/Mullite/Er2SiO5 New Environmental Barrier Coating at 1350℃
    FAN Jin-juan, CHANG Zhen-dong, TAO Chun-hu, WANG Fu-chi
    2014, 0 (10): 90-95.   DOI: 10.11868/j.issn.1001-4381.2014.10.016
    Abstract ( 744 ( PDF (2635KB)( 227 Citation
    Si/Mullite/Er2SiO5 environment barrier coatings (EBCs) were prepared by chemical vapor deposition and plasma spraying on SiC/SiC composites. The oxidation behavior of the coatings at 1350℃ was investigated,and the structure change of the coatings was analyzed by SEM,EDS and XRD. The results show that the oxidation kinetics of the samples coated by Si/Mullite/Er2SiO5 conforms to the logarithm law. The oxidation rate of the samples is high at the early stage of the oxidation duration,and then grows steady with the increase of the oxidation time. The coatings can serve up to 400h at 1350℃. The cause for failure of coatings is that the atom O diffused into the bond coat and substrate through the coatings to cause the oxidation of bond coat and substrate,and the bond strength then decreases to cause the peeling of the coating.The cracks perpendicular to the coating surface will be the route of air diffusion from the surface into the bond coat and substrate,and accelerate the oxidation failure of the coating.
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    Structure Change of CNT on the Surface of CNT/Steel Composite
    ZHOU Ze-hua, XIN Yong, ZENG Xiao-shu
    2014, 0 (10): 96-100.   DOI: 10.11868/j.issn.1001-4381.2014.10.017
    Abstract ( 724 ( PDF (1412KB)( 233 Citation
    The CNT/steel composite was fabricated by mixing molten steel with CNT/Al powder in a ladle. The composite and cast residue was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that CNTs are encapsulated by steel substrate. Pristine crooked CNTs are transformed into straight CNTs. A microstructure of highly aligned layers is achieved.This indicates that CNTs are highly graphitized when mixed with molten steel at 1550℃.
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    Influence of Fe-doping and Annealing Atmosphere on Crystalline Structure and Magnetism of TiO2 Thin Films
    GU Jian-jun, LIU Peng-fei, HAN Jin-rong, YANG Shu-min, HAN Wei, QI Yun-kai
    2014, 0 (10): 101-105.   DOI: 10.11868/j.issn.1001-4381.2014.10.018
    Abstract ( 692 ( PDF (1370KB)( 242 Citation
    Fe doped TiO2 thin films were fabricated on the glass substrates by DC magnetron sputtering,and were annealed in air and vacuum at 500℃ for 30min,respectively. The effects of Fe content and annealing atmosphere on the crystallization,the morphology and magnetism of TiO2 thin films were investigated.The results show that the Fe doped TiO2 thin films annealed in vacuum at 500℃ exhibit a amorphous structure,and no room temperature ferromagnetism is observed,but the samples annealed in air show good crystallization,and room temperature ferromagnetism is observed in all samples. With the increasing of Fe doping,the structure of the TiO2 thin films is changed from anatase to rutile.
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    Progress in Research on Chemical Strengthened Aluminosilicate Glass
    JIANG Liang-bao, LI Lei, ZHANG Guan-li, YAN Yue
    2014, 0 (10): 106-112.   DOI: 10.11868/j.issn.1001-4381.2014.10.019
    Abstract ( 945 ( PDF (1148KB)( 972 Citation
    The basic principle of chemical strengthening was presented,the factors that influence the strength of the chemically strengthened aluminosilicate glass were introduced from five aspects,including chemical strengthening temperature,chemical strengthening time,molten salt formulation and concentration,thermal fatigue and surface scratches. Common key scientific problems related with the chemical strengthening of aluminosilicate glass were analyzed in details. The application progress of chemically strengthened aluminosilicate glass on aircraft windshield and the existing problems were comprehensively reviewed,and the developing trend of chemically strengthened aluminosilicate glass was also predicted.
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