XIA Peng-cheng, YU Jin-jiang, SUN Xiao-feng, GUAN Heng-rong, HU Zhuang-qi. Influence of Solution Temperature on Microstructure and Stress Rupture Property of DZ951 Nickel-base Superalloy[J]. Journal of Materials Engineering, 2009, 0(9): 1-4.
The effect of solution temperature on microstructure and stress rupture property of DZ951 directionally solidified nickel-base superalloy was investigated by optical electron microscope,SEM and TEM.The results show that dendritic segregation decreases and the alloy strength increases after solution treatment.Carbide changes block from bone-like of as-cast alloy and discontinuously distributes in the grain boundary,which inhibits the initiation and propagation of cracks during stress rupture test.The size of γ′ phase reduces and γ′ distribution is more homogeneous after solution treatment.The stress rupture property of the alloy after solution treatment is improved.The stress rupture life of the alloy at the solution temperature of 1300℃ is higher because the distribution of alloy elements is more homogeneous and the γ′ volume fraction increases.
WANG Gui-feng, TIAN Zong-jun, HUANG Yin-hui, LIU Zhi-dong, GAO Xue-song. Fractal Growth of Ni Dendrite in Jet-electrodeposition with Point Anode[J]. Journal of Materials Engineering, 2009, 0(9): 5-8.
The growth process of quasi-two-dimensional dendrite cluster by electrodeposition with a point anode and circular electrolytic cell was successfully simulated by the growth model of dendrite founded based on fractal theory.Using point metal Ni as anode and circular graphite as cathode,two-dimensional dendrite of Ni was manufactured by jet-electrodeposition to test the simulation.The result shows that the dendrite of Ni has the character of fractal,it is similar to the results of simulation.The model mentioned above gives a very accurate depiction to the growth process of dendrite in electrodeposition and would be helpful to direct the experimentation of dendrite fractal growth.
GUO Qi-wen, CAI Hong-nian, WANG Fu-chi, CHENG Xing-wang, WANG Shu-chi, FAN Qun-bo. Construction of Index System of Materials Applicability Evaluation[J]. Journal of Materials Engineering, 2009, 0(9): 9-12.
Materials applicability evaluation(MAE) in the field of equipments is to evaluate the technology readiness levels(TRL) of materials and the rationality of materials usage.To construct the index system of MAE,the construction principle is firstly built.Secondly,the main influence factors of materials applicability are analyzed,including materials properties,technology maturity,support capabilities and economic affordability.Based on the work mentioned above,the evaluation index system with orderly hierarchy,which includes the necessary key factors of materials engineering application,is founded via the administrative analysis method.
ZHANG Wei, LIU Hui, LIANG Fang-hui, HUANG Yong-ling. Effects of Directional Solidification on Tensile Property of Femoral Stem with Porous Surface[J]. Journal of Materials Engineering, 2009, 0(9): 13-15,19.
Femoral stems with porous surface of hip joint prostheses were manufactured using biomedical Co-Cr-Mo alloys by usual casting and directional solidification casting,followed by sintering at high temperatures.Effects of two different casting processes on mechanical properties of femoral stems were studied.Macro-and micro-structure and fracture appearance were compared.The results indicate that for femoral stems manufactured by directional solidification followed by sintering,column crystals are observed and the tensile strength at room temperature increased greatly by the technology.The tensile strength and elongation of femoral stems with porous surface increased to 1.2 and 2.0 times,respectively.
ZHANG Xue-feng, LI Hui-rong, WU Zhao-yu. Influences of Rapid Annealing on Microstructure of BaSrTiO3 Thin Films[J]. Journal of Materials Engineering, 2009, 0(9): 16-19.
BaSrTiO3(BST) thin films were deposited by radio frequency magnetron sputtering,and then treated by rapid thermal annealing process.The influences of annealing temperature and time on the microstructure of the samples were explored by XRD and atomic force microscope(AFM).The results show that the strength of the diffraction peaks and the crystalline degree of BST thin films are all increased with the increase of annealing temperature.The surface roughness of the BST thin films decreases at first,and then increases with the annealing temperature increase.However,the grain size of the BST thin films decreases monotonously with the annealing temperature increase.With the increase of annealing time,the grain sizes are almost not changed at annealing temperature of 700℃.However,the surface roughness of the samples decreases monotonously with the increase of annealing time.
ZHOU Guo-hua, ZENG Xiao-shu, ZHANG Zhan, XU Qiang, LUO Chao. Effects of Temperature on Microstructure of CNTs/AZ31 Alloy Composites by Equal Channel Angular Pressing[J]. Journal of Materials Engineering, 2009, 0(9): 20-23.
In order to obtain optimum temperature of carbon nanotubes/AZ31 alloy composites in equal channel angular pressing(ECAP) process,at various temperatures carbon nanotubes/AZ31 alloy composites were prepared by means of ECAP and in the die with the intersecting angle Φ= 90°.The results indicate that a great deal of ultra-fine grains appear in carbon nanotubes/AZ31 alloy composites just after one pass of ECAP at different temperatures.At 220℃ the sample surface is smooth,it is conducive to the realization of multi-pass of ECAP.At the same time,grain refinement is obtained better results.
WANG Gui-long, ZHAO Guo-qun, LI Hui-ping, GUAN Yan-jin. Design and Analysis of Variotherm Injection Molding of Large LCD Panel Based on CAE[J]. Journal of Materials Engineering, 2009, 0(9): 24-28.
A variotherm injection molding technique with steam heating and coolant cooling was studied and its molding process was also designed.The thermal analysis model for a LCD panel mold was constructed to analyze the heating phase and cooling phase of the variotherm injection molding process.The variotherm molding process parameters for the production of the LCD panel was determined based on the thermal response simulation.Finally,a variotherm injection molding experimental production line of the LCD panel was designed and constructed to verify the numerical simulation results.The results show that surface mark of weld line is eliminated,and the gloss of the panel surface is also greatly improved.
YANG Cai-yun, HU Zhen-ying, ZHOU Hong-ying. Influence of 3D Woven Preform Architectures on Mechanical Properties of C/C Composites[J]. Journal of Materials Engineering, 2009, 0(9): 29-32,37.
Two different kinds of structural preforms were designed and manufactured using carbon fiber,which were 3D layer-to-layer angle-interlock weave(JLS)and 3D solid orthogonal panel weave(SZJ).C/C composites were made by chemical vapor infiltration(CVI) and liquid resin impregnation.The influences of preform architectures on mechanical properties of C/C composites were explored.The tensile and shear properties of two materials were measured and analyzed.The results show that there is great influence of reinforcement architectures on the mechanical properties of the C/C composites greatly,besides on tension broken model.The C/C composites reinforced by 3D solid orthogonal panel preform behave better in mechanical properties than that reinforced by 3D layer-to-layer angle-interlock preform.
HE Yong-gang, LI Ke-zhi, WEI Jian-feng, GUO Ling-jun, LI He-jun, ZHANG Lei-lei. Microstructure and Fabrication of C/C Composites at Super-short Gas Residence Time[J]. Journal of Materials Engineering, 2009, 0(9): 33-37.
The infiltration of 2D-needle bundle fiber preforms was studied by the novel isothermal chemical vapor infiltration technique(ICVI),natural gas as the carbon source gas,no diluent gas,at 1100℃ and absolute pressure 10kPa with gas residence time of 0.01,0.02,0.03s,respectively.The densification rules were analyzed by densification rate and radial-direction density distribution with different residence time.The textures of samples were observed by polarized light microscopy(PLM) and scanning electron microscopy(SEM).The results show that 2D preform can be densified from inside to outside at 1100℃ for 150h,with gas residence time 0.01s,the C/C composites have a higher bulk density of 1.75g/cm3.Simultaneously,the micrographs show that the double-layer textures of the pyrocarbon change from medium-textured(MT) to high-textured(HT),only lower 2μm thickness MT on the fiber surface.
LIU Guang, ZHANG Zhen-zhong, CHEN Qian, ZHANG Hao, YIN Chang-hao, ZHANG Shao-ming. Microstructures and Properties of Rapidly Solidified Mg-Zn-Y-Zr Alloy Ribbons[J]. Journal of Materials Engineering, 2009, 0(9): 38-41,46.
The Mg-5Zn-1Y-0.6Zr alloys were prepared by conventionally solidified method and rapidly solidified method.The solidification microstructures and properties of the alloys were observed by XRD,SEM and micro-hardness measurements.The results indicate that the conventionally solidified alloy is composed of preliminary α-Mg matrix and interdendritic ternary phases of I-(Mg3Zn6Y) quasicrystal phase and W-(Mg3Zn3Y2) phase in the grain boundary.The rapidly solidified alloys are composed of fine α-Mg matrix phase,amorphous phase and quasicrystal I-phase.The amorphous phase and ultra-fine phase are the main reason to increase the micro-hardness value of the alloy ribbon.With the increase of cooling rate,the micro-hardness of the rapidly solidified alloys increase tremendously.The maximum micro-hardness value of the rapidly solidified alloy is HV167.23,which is 2.2 times the size of the conventionally solidified alloy.
WANG Chao-hua, LIU Yi-jiang, ZHU Da-chuan, TU Ming-jing. Effect of Preparing Process of Ball-milling Solid Chemical Reaction at Ambient Temperature on Property of Nano-ATO Powders[J]. Journal of Materials Engineering, 2009, 0(9): 42-46.
Precursors were prepared by ball-milling solid chemical reaction using H2C2O4·H2O,SnCl2·2H2O,SbCl3 and NH4HCO3 as raw materials at ambient temperature.In the process of milling,the raw materials were milled,mixed round,thus leading to reacting with each other.So supper small precursors were prepared by dint of milling.Then antimony doped tin oxide(ATO) was obtained by thermal decomposition of the precursors.The effect of antimony content,thermal decomposition temperature,time,and pH on resistance of ATO was studied by means of XRD,SEM and measuring resistance.The results show that if pH is 8.5 by the end of milling,the azure spherical nano-ATO about 80nm will be obtained by decomposition of the precursor(10%Sb,mass fraction) at 900℃ for 2h after at 600℃ for 2h,whose resistance is 1.2Ω·cm.
CHEN Lin-heng, KANG Yong-lin, LI Xian-hao, WEN De-zhi, LIU Guo-min. Effects of Processing Parameters on Microstructures and Properties of Low-carbon Bainitic High Strength Steels Produced by CSP[J]. Journal of Materials Engineering, 2009, 0(9): 47-50,60.
The effects of controlled rolling and controlled cooling parameters on the microstructures and mechanical properties of low carbon bainitic high strength steels produced by CSP(Compact Strip Production) were investigated.Through comparing the influence of several hot-rolling processes on the microstructures and properties,the results indicated that with the decreasing of finish rolling and coiling temperature especially coiling temperature,the volume fraction of bainite in bainite-ferrite matrix increased.Moreover,much more finer microstructure,M-A islands and smaller dispersion precipitates were obtained by reducing the finish rolling and coiling temperature.Therefore the yield strength and toughness were improved.
GAO Huan-fang, ZHANG Sheng-tao, LUO Tian-yuan, QUAN Xue-jun, XU Jun-qiang, FANG Li. Phosphate Process and Performance of Zinc Phosphate Coating on AZ31B Magnesium Alloy[J]. Journal of Materials Engineering, 2009, 0(9): 51-55,65.
The anticorrosive performance and the morphology of zinc phosphate coatings on AZ31B magnesium alloy of different phosphating time and different phosphating temperatures were studied by Tafel and SEM.And the phase component and composition of zinc phosphate coatings which was formed at the best technological conditions were studied by XRD and EDS.Results indicate that the phosphating time and phosphating temperature are an obvious influence on the anticorrosive performance of zinc phosphate coatings on AZ31B magnesium alloy,the best phosphating time is 5min and the best phosphating temperature is 50℃;the phosphate coating consists of Zn3(PO4)2·4H2O,Zn2Mg(PO4)2 and a small quantity of Zn;Mg of AZ31B magnesium alloy is dissolved at microanode in zinc phosphating bath,but Al isn’t.Phosphating reaction mechanism on the AZ31B magnesium alloy surfaces was also investigated.
GU Yu-li, HE Yu-huai, TAO Chun-hu, ZHENG Fei, ZHANG Guo-dong. Low Cycle Fatigue Fracture Mechanism at Elevated Temperature for FGH96 Nickel-base Superalloy[J]. Journal of Materials Engineering, 2009, 0(9): 56-60.
Low cycle fatigue tests were conducted on FGH96 nickel-base superalloy with total strain amplitude from ±0.4% to ±0.8% at 550℃ and 720℃.The fatigue behavior and micromechanism of the alloy were studied through scanning electron microscopy(SEM) and transmission electron microscopy(TEM),and the correlations between the areas of fatigue propagation region and the cycles of fatigue were established.The results show that FGH96 fatigue fracture characteristic is brittle intergranular,the alloy possesses lower fatigue lifetime at higher temperature that is relevant to oxidation damage and cyclic deformation,the tests temperature plays an important role to fatigue lifetime and oxidation damage effect is evident when the strain amplitude is lower(<0.6%).The dislocation density is much higher at higher strain amplitude and the dislocation occurrs cross sliding and climbing.The relationship between logarithmic areas of fatigue propagation region and logarithmic fatigue lifetime is linear.
HUA Zhong, YANG Yu-rong, YUAN Yuan, YANG Yong-gang, CAO Xia, WANG Zhi-ying. Microstructure Evolution of Polyacrylonitrile Fibers During Preoxidation[J]. Journal of Materials Engineering, 2009, 0(9): 61-65.
The cross-section character and microstructure of polyacrylonitrile fibers which were preoxided gradually at 200-275℃ were investigated by means of scanning electron microscope(SEM),wide angle X-ray diffraction(WAXD),small angle X-ray scattering(SAXS).Based on the WAXD and SAXS data of different specimen,the crystallite size,micropore size,volume fraction of small micropore and micropore fractal dimension were calculated respectively.The change of microstructure during preoxidation was also analyzed.Results showed that as the preoxidation temperature increased,the crystallite size of fibers increased and then decreased,while the micropore size of fibers decreased and then increased,volume fraction of small micropore increased gradually,micropore fractal dimension reduced and then increased.
XU Cong-min. Electrochemical Corrosion Behavior of X80 Pipeline Steel in Simulated Medium of Saline-alkali Soil[J]. Journal of Materials Engineering, 2009, 0(9): 66-70.
The corrosion behavior and mechanism of X80 pipeline steel was investigated in simulated solution of saline-alkali soil using electrochemical measurement,scanning electron microscopy(SEM),energy dispersive spectrum(EDS) and X-ray diffraction(XRD).Effects of heat treatment and corrosion time on the polarization curves were analyzed.The results show that the change of microstructure by anneal treatment accelerated the corrosion of X80 steel.The corrosion rates and pitting sensitivity increase both original and anneal treatment state.The cathodic processes are dominated by the oxygen activation control.The corrosion product is basically FeOOH(surface layer) and Fe3O4(inner layer).The integrality and compactness of corrosion product films influenced the corrosion behavior and process,increased the corrosion damage of X80 steel surface.The content of Cl- dominated the corrosion severity.
CHEN Liu-ding, TONG Xiao-yan, YAO Lei-jiang, CHENG Qi-you. Influence of Open Hole on Mechanical Behavior of Plain-woven C/SiC Ceramic Matrix Composites[J]. Journal of Materials Engineering, 2009, 0(9): 71-74.
Tension,compression and fatigue experiments were performed to investigate the mechanical behavior of plain-woven C/SiC composite specimen with open hole compared with that of smooth specimen.The fracture surfaces of specimens were observed by scanning electron microscope(SEM) and optical microscope(OM) to analyze its damage mechanism.The results indicate that,the response of plain-woven C/SiC ceramic matrix composite specimen with open hole under tensile loading is nonlinear to rupture and the same as that of smooth specimen,tensile strength decreases by 11.8% and tensile fracture strain decreases by 54.3%.The response of specimen with open hole under compression loading is different from that of smooth specimen,it is linear at low stress level and then becomes nonlinear due to obvious crack closure effect.Compression strength decreases by 12.2% and compression fracture strain decreases by 54.9%.Fatigue limite of specimen with open hole is 88% of its ultimate tensile strength and equivalent to that of smooth specimen.The specimen with open hole has low stress concentration factor and hence has low sensitivity to open hole.The fracture surfaces all go across the center of open hole.Damage appears at the hole edge where has severe stress concentration effect.The direction of fracture surface is related to the initial imperfection of open hole.
CAO Tong-kun, GAO Wei. Wear Behavior and Mechanism of Self Tribofilm Formation of Al2O3/TiC/CaF2[J]. Journal of Materials Engineering, 2009, 0(9): 75-79.
Al2O3/TiC/CaF2/TiC ceramic composites with the addition of CaF2 solid lubrication were produced by hot pressing.Sliding wear tests against cemented carbide were performed on the ceramic composites using ring-block method.The mechanism of tribofilm forming was studied.Results showed that the friction coefficient decreased with the increase of CaF2 content,while the wear rate decreased with the increase of CaF2 content up to 10%(mass fraction),with further increases in CaF2 content,the wear rate increased rapidly.A self tribofilm with a smooth surface formed on the wear surface.The self tribofilm acted as solid lubricant film between the sliding couple,thus significantly reduced the friction coefficient.The tribological hot and mechanical press in the tribological process could release CaF2 solid lubricant on the worn surface.When much CaF2 solid lubricant were released and smeared on the worn surface,tribofilm were formed.Cracks were found on the surface of the self tribofilm under repeated frictional condition because of the mechanical stress and thermal stress.After tribofilm falling off,tribofilm will be reformed on the surface,thus the tribofilm runs into a forming,destroying,falling off,reforming circle.
WANG Hong-yu, ZUO Dun-wen, MA Hao, WANG Ming-di, LU Ying-yan. Effects of Process Parameters on Microscopic Qualities of Coatings Formed by Squash Presetting Type Laser Cladding[J]. Journal of Materials Engineering, 2009, 0(9): 80-83,88.
A novel powders presetting method,namely squash presetting method,is presented to overcome the shortcomings of existing methods.The presetting of powders on the substrate was environmental friendly performed by the method,and laser cladding coatings were prepared by crosscurrent CO2 laser using different process parameters.Status of interfacial bonding,dilution and microstructure of the coatings were observed and determined with OM and SEM,and effects of process parameters on microscopic qualities of the coatings were revealed.The results show that big spot diameter is beneficial to the energy absorption of substrate in the case of definitive thickness of presetting layer,which promotes the forming of metallurgical bonding between coating and substrate.When spot diameter is same,high power and low scanning speed are beneficial to the improvement of interfacial bonding performance.With the increase of power density,the dilution of cladding layer increases as power density is less than 1000W/mm and decreases as power density is more than 1000W/mm.However,when power density is more than 1000W/mm,the using efficiency of laser energy is in a low level.Moreover,columnar dendrite in the top section of cladding layer changes into cellular microstructure while the power density decreases.Therefore,the parameter with big spot diameter,low power and slow scanning speed should be adopted in squash presetting type laser cladding.
FENG Xian-xian, ZHAO Xiao-ru, LIU Kai, LIU Bo, ZHAO Liang. Development of Novel Transparent Conducting Oxide Nb-doped TiO2 Films[J]. Journal of Materials Engineering, 2009, 0(9): 84-88.
Novel transparent conducting oxide Nb-doped TiO2 thin films are currently studied by researchers as hot materials due to their excellent optical and electrical properties.The optical and electrical properties and mechanism of Nb-doped TiO2 films were analyzed.Meanwhile,the effect factors on the optical and electrical characteristics,the current research developments,and the future work were summarized.Especially,the effect of carrier density and scattering process on optical transmission and conductivity was discussed.
