ZHOU Yuan, MAO Wei, LI Xiao-hong. Microstructure and Mechanical Properties of Single Crystal Superalloy DD6 Joint Brazed with BNi82CrSiB Filler Metal[J]. Journal of Materials Engineering, 2007, 0(5): 3-6.
The single crystal superalloy DD6 was bonded by vacuum brazing at 1070℃ for 15min using the BNi82CrSiB filler metal.The sound joint was obtained.The result showed that the elements of the filler metal did not diffused into the base metal.At 750℃,the joint tensile strength reached about 400MPa,and the stress-rupture strength of 750℃/100h was 100MPa.The rupture of joint originated from the compound phases in the central part of the brazing seam,and the tested samples exhibited brittle fracture.
WANG Jun-li, WANG Rui, LI Zhi, ZHONG Ping. Formation of Order Phase in 23CoNi Steel and Its Effects on Mechanical Properties[J]. Journal of Materials Engineering, 2007, 0(5): 7-10.
The small and dispersed order phase B2 was observed in 23CoNi steel by TEM.The lattice parameters of the phase were close to that of matrix in the alloy.Tempering at 485-600℃,the size of order phase grew up as tempering temperature going up.The main reason of the formation of the order phase was related to the content of Ni,Al and Ti.High tensile strength was kept as tempered from 440℃ to 490℃ in the heat,this phenomenon may be attributed to the formation of the order phase.
WU Xiao-qing, LI Jia-lu, CHEN Zu-pan. Influence of Finite Element Mesh on Mold-filling Simulation in RTM[J]. Journal of Materials Engineering, 2007, 0(5): 11-14,18.
The computer code was developed based on finite element/control volume method.The influence of the node number and mesh density on the filling mold was studied using the code.Flow front,filling time and dry spot were simulated and analyzed through comparing different mesh density and injection location such as the shape of the rectangle with hole.The result shows that calculating time is prolonged and the effect on the filling time is slight when node number increases a certain degree.The location of the flow front is influenced by mesh density.The number and location of the dry spot are confirmed according to the shape of the flow front.
WU Shi-ping, YANG Fei-yu, ZHANG Xing-hong, DU Shan-yi. Effects of Short Carbon Fiber on Mechanical Properties of ZrB2-SiC Ultra-high Temperature Ceramics[J]. Journal of Materials Engineering, 2007, 0(5): 15-18.
Zirconium diboride-silicon carbide based ceramics are attractive for application in aircraft propulsion systems and thermal protection system for hypersonic vehicle because of their high melting point,high thermal and electrical conductivity and good chemical stability.However,the major problems associated with ZrB2/SiC are lack of damage tolerance and insufficient strength as structure components.ZrB2-20%(volume fraction) SiC ceramics with the additional short carbon fiber was developed to promote graceful failure using hot pressing technique. The results show that the introduction of short carbon fiber into the ZrB2-20%SiC matrix results in an apparent increase in fracture toughness from 2.0MPa·m1/2 to 6.56MPa·m1/2 and not evidently change in flexural strength from 502MPa to 445MPa and elastic modulus from 414GPa to 322GPa.Meanwhile the influence of short carbon fiber on the strength,and modulus is analyzed and estimated using a modified role-of-mixture formulation and that on the toughness is also calculated based on the toughening mechanisms of crack bridging,fiber pullout and crack deflection.The calculated results of the strength,elastic modulus and fracture toughness of the composite agree well with the experimental results.
LIU Yan, SUN De-zhi, LI Lei. Characterization and Catalytic Activity of Fe2O3/γ-Al2O3 Catalyst[J]. Journal of Materials Engineering, 2007, 0(5): 19-23.
Fe2O3/γ-Al2O3 catalyst was prepared by impregnation method.BrunauerEmmett-Teller surface area analyzer(BET),scanning electron microscope(SEM),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS) and X-ray fluorescence spectroscopy(XRF) techniques were performed to characterize Fe2O3/γ-Al2O3 catalyst.The catalytic activity of the prepared catalyst was investigated by catalytic wet peroxide oxidation process(CWPO)at room temperature and atmospheric pressure,and azo dye,C.I.acid orange 7 was selected as a model pollutant.The results showed that α-Fe2O3 was detected by XRD technique and the mass fraction of Fe was 1.907% in Fe2O3/γ-Al2O3 catalyst.The 82.10% color removal efficiency,80.14% COD removal efficiency and 74.2% TOC removal efficiency of 500mg/L acid orange 7 could be attained in 3h with 30g/L Fe2O3/γ-Al2O3 and 330mg/L H2O2.Compared with the traditional Fenton system,the higher mineralization efficiency was achieved by using catalytic wet peroxide oxidation(CWPO) process when Fe2O3/γ-Al2O3 was used as a catalyst.In addition,the catalysts used in CWPO process could be separated easily from solution and reused.
LI Wei, CHEN Zhao-hui. Microstructure and Permeability of Cf/SiC Composites Fabricated via Precursor Infiltration and Pyrolysis[J]. Journal of Materials Engineering, 2007, 0(5): 24-27.
Bubble point method and SEM were applied to evaluate the inner structure and permeability of 3D braided and 2.5D Cf/SiC composites,fabricated by precursor infiltration-pyrolysis(PIP) process.The results show that the porosity of the composites is 10%-20%,the pore sizes range from hundreds micrometers to less than one,and the average sizes of the open paths through the samples are not larger than 10μm.The braiding/weaving architectures have great effects on the pore structure,pore size distribution and permeability,and the permeabilities increase with the open paths’sizes,while have no direct relations with porosity.
ZHANG Guo-dong, YU Hui-chen, HE Yu-huai, SU Bin. Effects of Specimen Dimension on Thermomechanical Fatigue Life in DS Superalloy DZ125[J]. Journal of Materials Engineering, 2007, 0(5): 28-30,35.
Thermomechanical fatigue(TMF) life of three temperature-strain phase angles and two specimen dimensions was studied in directional solidification(DS) superalloy DZ125.The results showed that fatigue,creep and oxidation damage always developed during TMF,temperature gradient occurred on surface and inside of specimen.Specimen dimension affected TMF life in DS superalloy DZ125.At high strain levels with shorter fatigue life,there were no evidence difference between TMF life of 8mm diameter specimen and fatigue life of 6mm diameter specimen.At low strain levels with longer fatigue life,TMF life of 8mm diameter specimen is longer than that of 6mm diameter specimen.
ZHANG Hui, SHEN Lan-ping, ZHAN Jian-chao. Electroless Silver Plating of Polyester Fabric with Different Reducing Agents and Its Electromagnetic Shielding Properties[J]. Journal of Materials Engineering, 2007, 0(5): 31-35.
Electroless silver plating on polyester(PET) fabric was operated using AgNO3 in the presence of different reducing agents in the lab respectively.The Ag-coated fabric was investigated by means of SEM,EDX,XRD and XPS and the electromagnetic shielding performance was also measured.The results showed that C12H22O11 was the most suitable reducing agent inducing high quality coating structure and the crystal size was relatively small compared with H2NNH2,KNaC4H4O6 and HCHO.As the chemical reaction was not carried out completely using C6H12O6 on the surface,the shielding effectiveness(SE) was greatly influenced.The SE increased at first,and then reached to a certain level with mass gain rate.
ZHANG Wei. Growth Kinetics of Voids Along Interface Between Al2O3 and Aluminized Layer of Aluminized Steel[J]. Journal of Materials Engineering, 2007, 0(5): 36-38,42.
The growth process of voids along the interface between Al2O3 and aluminized layer during oxidation at 1000℃ was investigated by high temperature oxidation test and scanning electron microscopy(SEM),X-ray diffractometer(XRD).The growth mechanism of interfacial voids was also discussed.The results showed that the growth of interfacial voids was controlled by oxidation process and there were corresponding relations between growth rate of the voids and oxidation rate of the surface for aluminized layer.The growth kinetics of interfacial voids accorded with a parabola growth rule and number of voids in unit area first increased quickly and then declined gradually with oxidation time.
BI Xiao-qin. Effects of Technology Parameters on Microstructure and Properties of Ni-SiC Composite Coatings[J]. Journal of Materials Engineering, 2007, 0(5): 39-42.
The Ni-SiC composite coatings on the iron-based sample were prepared by the composite electrodeposition.The effect of the granularity and content of SiC and the voltaic consistency on the microstructure and microhardness of the composite coatings was studied.The results showed that the coating with little granular SiC was close and even,and the coating with big granular SiC was rough,which a little of SiC was not packed completely by Ni alloy.With increase of the SiC concentration,the content of SiC in the coatings rose accordingly under the condition of the same granularity.With increase of the SiC granularity,the microhardness of the coatings reduced in the definite range of SiC concentration.The microhardness of the coatings went up with increase of the SiC concentration and the voltaic consistency.
LU Ya-lin, LI Miao-quan. Deformation Behavior and Modeling of Semi-solid Al-4Cu-Mg Alloy[J]. Journal of Materials Engineering, 2007, 0(5): 43-47.
Effects of deformation temperature and strain rate on deformation behavior of semi-solid Al-4Cu-Mg alloy were investigated.The results show that deformation temperature and strain rate are significant effect on peak stress of Al-4Cu-Mg alloy rather than steady flow stress,which result from different deformation mechanism.At the beginning of compression,the deformation mechanism is liquid flow(LF) and flow of liquid incorporating solid particles(FLS).However,with the increasing of height reduction,sliding between solid particles(SS) and plastic deformation of solid particles(PDS) are dominating in the semi-solid compression.On basis of the experimental data of semi-solid Al-4Cu-Mg alloy,a model was established to describe the relationship between the processing parameters and flow stress,which shows good match with experimental data.
LIU Ming, MA Jian, ZHANG Bao-gang. Preparation and Properties of Rare-earth Doped Luminescent Glass[J]. Journal of Materials Engineering, 2007, 0(5): 48-52.
The new-type long persistent phosphorescence powder CaxSr1-xAl2O4:Eu2+ was synthesized by the conventional solid phase reaction method in reducing atmosphere.And then two kinds of luminescent glasses were synthesized.Glass1 was prepared by doping the luminescent powder in the pure borate glass B2O3-(Na,K)2O-XO and Glass2 was grown by doping the luminescent powder in borated silicate glass SiO2-B2O3-(Na,K)2O-X2O-XO.This experiment put forward two stages heat treatment method which improved homogenization and transparency of the luminescent glass and determined the optimal sintered temperature 820℃ and 880℃ respectively.By SEM and the contrast analysis on the surface quality and luminescent intensity of Glass1 and Glass2,it is found that the stability and luminescent effect of Glass2 from borated silicate glass is better than that of Glass1 from borate glass.
XU Wei-ping, XING Li, KE Li-ming. Microstructural Evolution of Nugget Zone in Magnesium Alloy AZ80A Friction Stir Welds[J]. Journal of Materials Engineering, 2007, 0(5): 53-56.
The effect of the observed microstructural evolutions of the nugget zone in magnesium alloy AZ80A friction stir welds(FSW) was discussed by using the new technique of orientation imaging microscopy(OIM).The results showed that there were the cyclical natures of the grains size,pole figures,inverse pole figures and the distribution of misorientation.It was concluded that recrystallized grains in the nugget zone formed by a continuous dynamic recrystallized mechanism.
FANG Xiao-qiang, LI Miao-quan, LIN Ying-ying. Finite Element Simulation of Equal Channel Angular Pressing of Ti-6Al-4V Alloy[J]. Journal of Materials Engineering, 2007, 0(5): 57-60,65.
With the help of finite element method,the distribution of equivalent strain,extrusion load during the isothermal equal channel angular pressing(ECAP) of Ti-6Al-4V alloy under different shear factor of friction,channel and corner angle were studied.The results showed that the increasing factor of friction caused the strain concentration,since the maximum load was improved 2.37 times than that of no friction, when the shear factor of friction was 0.5.Increasing channel angle was beneficial for decreasing load and deformation homogeneousness,but reducing equivalent strain in each pass.In addition,decreasing corner angle was beneficial for increasing the extent of the homogeneous deformation,but exhibited severe strain concentration near the corner angle.
YE Tu-ming, YI Jian-hong, PENG Yuan-dong, XIA Qing-lin. Characteristics of Warm Compaction in Powder Metallurgy and Its New Developments[J]. Journal of Materials Engineering, 2007, 0(5): 61-65.
This paper outlined its technical characteristics and new developments of warm compaction,for example,warm flow compaction,heat-die compaction etc.It was pointed out that conventional warm compaction might be replaced by heat-die compaction on account of its simples procedures and lower compaction temperature in the future.And heat-die compaction,which representative was AncorMax D processing,would be a very promising method for high-density PM parts.
