航空材料学报

Effect of P on Oxidation Behavior of Thermo-Span Low Expansion Superalloy at 650℃

SUN Ya-ru, SUN Wen-ru, SUN Xiaofeng, GUO shou-ren, LIU Zheng, HU Zhuang-qi

2008, 28(1): 1-4.

[Abstract](1028) [PDF 576KB](167)

Abstract:
Using thermogravimetry(TG) and scanning electron microscope equipped with electron probe(EPMA),the effect of trace element phosphorus on oxidation behavior of Thermo-Span alloy at 650℃has been investigated.The results show that oxide behavior follows the parabolic curve rule.The oxidation layer is compose of both outer oxidation layer and transition layer, Fe,Co and O elements are enriched in oxidation outer layer,Al,Cr and Nb elements are enriched in the transition layer,and the content of Fe,Co decrease.0.023% phosphorus element can accelerate not only needle oxidation of Fe,Co turn into massive oxidation of Co in outer layer,but also inhibit Fe migrate toward to outer layer and O elements to transition layer.In addition,it can be found that 0.023% phosphorus element can decrease the oxidation rate of the Thermo-Span alloy at 650℃ and increase its oxidation resistance.

Microstructure and Mechanical Properties of Ti/Ti-Al Multi-layered Composite Prepared by EB-PVD

MA Li, SUN Yue, HE Xiao-dong

2008, 28(1): 5-8.

[Abstract](1227) [PDF 1293KB](205)

Abstract:
A multi-layered metal/intermetallic thin sheet consisting of Ti and Ti-48at%Al has been prepared using a high powerful electron beam physical vapor depositing technology.The effects of target-substrate distance,microstructural parameters and the selecting position of samples on the mechanical properties were explored.Then the tensile properties of Ti/Ti-Al microlaminates at different temperature was studied and evaluated.The test results shows that the room-temperature brittleness have been improved and the properties at the range of 500～800℃ are favourable by the abnormal strengthening effect of intermetallic layers

Study of Catalysis Effect of Ni on CVI PyC Process

XU Piao, CHENG Lai-fei, ZHANG Li-tong, XU Yong-dong, TONG Chang-qing

2008, 28(1): 9-12,17.

[Abstract](1164) [PDF 645KB](230)

Abstract:
Nickel was infiltrated into the carbon/silicon carbide(C/SiC) composite by liquid impregnation and reduction method.The influence of nickel on the process of chemical vapor infiltration of carbon has been investigated.The catalysis of nickel was studied by weight analysis,the microstructure of the material was observed by SEM and the composition was analyzed by XRD.The results shows that nickel infiltrated into C/SiC composites accelerates the deposition of carbon in the material.The mass gain rate of carbon reached the maximum(9.98%) when nickel content was 4.4%.The carbon deposited is aggregative state consisting of fine particles.During CVI process,nickel reacts with silicon carbide to form Ni2Si and Ni3Si.

Study on Preparation and Structure of Gigantic Magnetoresistivity Materials(La_1-xGd_x)_2/3Ca_1/3MnO₃ Compounds

LUO Guang-sheng, LIU Guang-hua, ZHOU Zheng-you, GAN Jian-ping, OUYANG Xiao-lü

2008, 28(1): 13-17.

[Abstract](1178) [PDF 738KB](261)

Abstract:
The samples of(La1-xGdx)2/3Ca1/3MnO3 and La1-xZnxMnO3were prepared by solid-state reaction method.Five samples of La2/3Ca1/3MnO3 compounds were sintered at the temperature range from 1200℃to 1400℃for 12 hours respectively,and two same groups of samples(La1-xGdx)2/3Ca1/3MnO3(x=0.2,0.4,0.6,0.8,1.0) compounds were sintered at the temperature 1350℃ for 12 and 24 hours respectively,and samples La1-xZnxMnO3(x=0.1,0.5,0.9) compounds were sintered at the temperature 1350℃ for 24 hours.The structure and the surface micro-structure of these samples were studied by the X-ray diffraction patterns and the SEM photograph,respectively.It is showed by X-ray diffraction patterns that all samples structure keep same perovskite structure with space group Pnma,but that the lattice parameters and the cell volume of the samples(La1-xGdx)2/3Ca1/3MnO3 and La1-xZnxMnO3 compounds change and the impure phase appear with the doped contents increasing.The magnetoresistance materials are sensitive to the structure,and hence the magnetoelectric properties change.From the SEM photograph it is exhibited that the surface structure of the samples of La2/3Ca1/3MnO3 compound sintered at the temperature 1400℃ is the perfect.

Hot Deformation Behavior and Microstructure Evolution of TC11 Alloy with Lamellar Structure

CHEN Hui-qin, GUO Ling, CAO Chun-xiao

2008, 28(1): 18-22.

[Abstract](1174) [PDF 2047KB](300)

Abstract:
The hot deformation behavior and microstructure evolution of TC11 with β-transformed lamellar structure were studied in the temperature range 800~980℃ and strain rate range 0.001~0.1s-1 by hot compression tests.Characteristics of Stress strain curves of the alloy deformed with the test parameters were analyzed.Kinetics analyses indicate that the stress exponent Controued and deforming activation energies in α+β region are 4.42 and 490.8kJ·mol-1 respectively,which indicate that deformation would be occurred by glide and climb of dislocation.Microstructure observation indicates that globularization and kinking of lamellar structure is the reason of flow softening.Deformation temperature and strain rate affect globularization processes severely.Globularization processes will progressed sufficiently at 980℃,0.001 s-1 or 0.01s-1,and 950℃,0.001 s-1.Logarithm of equiaxed a diameters at steady state has linear relationship with logarithm of Z parameters during globularization processes at 900~980℃ and 0.001~0.1s-1.

Microstructure Evolution of 2J4 Alloy Deformed by ECAP

DU Zhong-ze, WU Lai-zhi, FU Hanguang, WANG Qing-juan, WANG Jing-tao

2008, 28(1): 23-29.

[Abstract](1207) [PDF 1342KB](248)

Abstract:
The equal channel angular pressing(ECAP) of 2J4 alloy was studied at room temperature with route A in which the sample was not rotated after pressing one pass and entered directly the next pass.The evolution of microstructure of 2J4 alloy after ECAP was investigated by means of optical microscopy(OM) and transmission electron Microscopy(TEM).The results show that the total equivalent true strain of 2J4 alloy is about 3.0 after ECAP,which is corresponding to the depressing amount of 90%.After one pass ECAP,the grain of the alloy changed into the lath martensite of 0.35μm in width and 2.5μm in length from 30μm in diameter.When the deformation pass increased,the martensite refined farther and the lath martensite transformed into the equiaxed grains.Moreover,the amount of α phase increased along with the increase of deformation amount.

Structure and Property Research on TiAl/NiCoCrAl Multilayer Composites Fabricated by EB-PVD

ZHANG Ru-bing, CHEN Gui-qing, ZHANG De-ming, YAO Zhen-zhong, ZHANG Xing-hong, HAN Jie-cai

2008, 28(1): 30-34.

[Abstract](1191) [PDF 1622KB](317)

Abstract:
TiAl/NiCoCrAl multilayer composites with 150mm×100mm×0.4mm were fabricated successfully by EB-PVD process.The phase composition,fracture morphology and mechanical properties of TiAl/NiCoCrAl multilayer composites were compared with that of one-layer TiAl alloys.The results indicate that NiCoCrAl layer of TiAl/NiCoCrAl multilayer composites mainly consist of Ni3Al and NiCrCo,and the TiAl layer is composed of γ,α2 and τ phase,but no delamination existed in the one-layer Ti-Al alloys is found.TiAl/NiCoCrAl multilayer composites have higher bending strength and better ductility than one-layer TiAl alloys.Compared with the TiAl-based alloys sheet,the fractures of the TiAl/NiCoCrAl multilayer composites are diverted from the manner of brittle intergranular fracture to the mixed manner of brittle intergranular fracture with some ductile transcrystalline fracture.The strengthening mechanisms of the TiAl/NiCoCrAl multilayer composites are the fine grained dispersion strengthening,and the toughening mechanisms are the crack deflection,the micro bridge join and the crack bend toughening.

Effect of Heat-Treatment on Impact Fracture Surface of High Co-Ni Ultrahigh Strength Steel

LI Jie, WANG Li, LI Zhi, ZHANG Jing-hai, YAN Ming-gao

2008, 28(1): 35-39.

[Abstract](1178) [PDF 1420KB](276)

Abstract:
The effect of solution and tempering temperature on the Charpy V impact energy AKV and HRC of ultra-high strength steel 23Co14Ni12Cr3Mo was studied,impact fracture surfaces were observed by SEM,and the undissolved carbide was analyzed by TEM.The results showed that in the range of 850~930℃ for solution,impact energy AKV increased with increasing temperature,HRC reached a peak value and then drop,while AKV increased and HRC decreased with increasing temperature,when tempered at 454~510℃.Dimples were observed on the transgranular fracture surface,where existed M23C6 type carbide particles.The higher the solution temperature,the less the particles.Properties of this steel could be improved by increasing solution temperature.

Laser Clad WC_p/Ni-Si-Ti Composite Coatings

FAN Ding, SUN Ming, SUN Yao-ning, ZHANG Jian-bin

2008, 28(1): 40-44.

[Abstract](1243) [PDF 792KB](262)

Abstract:
Using laser cladding technique,Ni3(Si,Ti) matrix composite coatings reinforced by WC and in-situ synthesis TiC multi-ceramics were fabricated by preplacing Ni78Si13Ti9(at%) powders containing three different WC contents on the nickel-matrix superalloy substrate.By means of SEM,EDS and XRD,microstructures of the coatings were investigated,and micro-hardness were measured.The results showed that excellent metallurgical bonding between the coatings and the substrates was obtained.Phases of the coatings are mainly composed of gamma Ni(Si) solid solution,Ni3(Si,Ti),WC-TiC multiceramics.With increasing WC percentage,content of carbides formed in the coatings increases,but porosity is also enhanced.The main morphologies of ceramics evolve from irregular polygonal shape to petal like shape,then irregular polygonal shape coexisting with petal like shape.

Effect of Welding Parameters on Formation of Double-focus Welds

LI Xiao-hui, WANG Su XIA Cai-yun

2008, 28(1): 45-48.

[Abstract](1155) [PDF 564KB](396)

Abstract:
A self designed welding head is described.The welding head can divide one torch into two equally and the two focuses are in series along the weld.A series of experiment has done by this head to analyze the effect of welding parameters on the formation and penetration of welds in double focuses laser welding.The experiment results indicate that the weld quality is improved prominently and crack sensitivity is reduced.There are many factors having effect on the formation and penetration of welds of double focuses laser welding,and also having influence on the microstructures and macro forms of welds.In all the parameters,the laser beam power and the wielding speed are the most primary factors.

Preparation of Square Crystalloid Nano-size Barium Titanate Powder by Improved Oxalate Coprecipitation Method

HOU Tie-cui, LI Zhi-Hui, LU Hong-xia, ZENG Zhao-huan

2008, 28(1): 49-52.

[Abstract](1264) [PDF 1088KB](271)

Abstract:
Square crystalloid nano-size barium titanate powders were prepared by an improved oxalate coprecipitation method,since the phase would go far away the square crystalloid when the powders' size was reduced by traditional technics.Square crystalloid nano-size barium titanate powder can be obtained after being calcined at 700℃ by the improved oxalate coprecipitation method;the calcining temperature would be lower about 100℃ than the routine oxalate coprecipitation method.Average size of the powder is about 30nm with equality dimension and the powders have thermal stability.

Intergranular and Exfoliation Corrosion Behaviour of High Strength Al-Zn-Cu-Mg-Zr Alloy Containing Sc

LI Wen-bin, PAN Qing-lin, ZOU Liang, LIANG Wen-jie, HE Yun-bin, WANG Chang-zhen

2008, 28(1): 53-58.

[Abstract](1246) [PDF 1731KB](301)

Abstract:
Intergranular and exfoliation corrosion behaviors of Al-Zn-Cu-Mg-Zr alloy containing Sc were investigated.This over-aged alloy has the lowest intergranular and exfoliation corrosion sensitivity which decreased with the aging time and accorded with the results of polarization tests in EXCO solution.intergranular and exfoliation corrosion are closely attributed to η',S' and their distributions.With the aging time prolonging,η' and S' phases precipitated and transformed into equilibrium η' and S' phases.The coarsed η' and S' phases not only decreased the anodic tunnels of intergranular corrosion but also reduced the open circuit potentials between the precipitated phases and Al matrix which minimized the intergranular and exfoliation corrosion rate in Al-Zn-Cu-Mg-Zr alloy containing Sc.

Development of Pmma Transparent Nanocomposites

CHEN Lu-song, HUANG Zheng-ming, DONG Guo-hua, HE Chuang-long

2008, 28(1): 59-64.

[Abstract](1281) [PDF 1094KB](397)

Abstract:
Co-axial electrospinning technique is utilized in preparing core-shell composite nanofibers,in which the shell material is PMMA and the core is PA-6.After a hot press treatment,the molten PMMA functions as resin matrix while PA-6 nanofibers as reinforcing material,resulting in a nanofiber reinforced transparent composite.Experiment results show that mechanical performance of the nanofiber reinforced composite is obviously improved without a significant influence on its transparency.Morphological and structural characterizations for the composite nanofibers and the transparent composites are realized in terms of SEM,TEM and FTIR.From the SEM pictures of the fractured composite samples,the effect of PA-6 reinforcing nanofibers on their mechanical and transparent behaviors is analyzed and discussed.

Research on Preparation and Thermophysical Properties of Dy₂ Zr₂ O₇ Ceramic Powder

ZHOU Hong-ming, YI Dan-qing

2008, 28(1): 65-70.

[Abstract](1177) [PDF 1364KB](486)

Abstract:
Dy2Zr2O7 composite ceramic powders used for thermal barrier coating were prepared by the coprecipitation-calcination method.The chemical compositions of the powders were analyzed by means of Inductively Coupled Plasma-Atomic Emission Spectrometry(ICP-AES).The microstructure and crystallographic phases of Dy2Zr2O7 were determined by SEM and X-ray diffraction technique.Dfferential Scanning Calorimetry(DSC),TG and XRD were used to analyze the crystallogrphic phase and the phase stability of Dy2Zr2O7.The Hall flowmeter was performed to determine the flowability of Dy2Zr2O7 powder.High-temperature dilatometer,DSC and laser thermal diffusivity methods were used to analyze its thermal expansion coefficient(TEC),specific heat and thermal diffusivity respectively.The results showed that the compositions of the prepared ceramic powders were in the range of the synthesis of Dy2Zr2O7 with fluorite structure,the Dy2Zr2O7 powders kept the fluorite structure and there was no phase transformation for Dy2Zr2O7 at high temperatures(~1350℃).The flowability of Dy2Zr2O7 powder calcined at 1400℃ was greatly improved.The TEC of the ceramic was slightly higher than that of conventional Y2O3-8wt.%ZrO2(8YSZ) and the thermal conductivity of the ceramic was much lower than that of 8YSZ,which indicated that Dy2Zr2O7 might be a excellent material for thermal barrier coatings.This study can provide science information for this material used as thermal barrier ceramic materials.

Synthesis,Characterization and Properties of Novel Latent Thermal Catalyst for Epoxy Resin

LIU Yu-yan, HE Li-na, WAN Zhi-min, DU Xing-wen

2008, 28(1): 71-75.

[Abstract](1314) [PDF 1229KB](245)

Abstract:
Latent thermal catalysts,aluminum tris(octadecylacetoacetate) was synthesized.The synthesized catalyst fulfills requirements for long storage stability at room temperature and a rapid cure at a moderately elevated temperature in curing epoxy resins.The thermal behavior,the molecular structures,the purity of aluminum compounds were characterized by differential scanning calorimeter(DSC),FT-IR spectrum,1H-NMR spectrum and element analysis.The cure system,thermal latency and mechanical properties of epoxy ZH 92-21/ 4,4'-Dihydroxydiphenylsulfone/aluminum tris(octadecylacetoacetate) system were also investigated.The viscosity of the resin system showed little change after 7 months and the phase change of the resin system led to a long shelf life.

Self-assembly Investigation of Aromatic Thiols at Interface of Carbon Fiber/Epoxy Composites

HE Jin-mei, HUANG Yu-dong, LIU Li, KONG Ling-yan

2008, 28(1): 76-81.

[Abstract](1208) [PDF 1325KB](294)

Abstract:
A new method based on the molecular self-assembly was proposed for the carbon fiber surface modification.The carbon fiber surface was first metallized by electroless Ag plating and then covered by organic compound self-assembly films.The surface-enhanced Raman scattering spectroscopy(SERS) analysis verified that two aromatic thiols with different end-groups chemisorbed onto the Ag-plated carbon fibers and formed a lie-down phase and tilt-angle phase corresponding to the substrate surface.XPS further proved the chemisorption of self-assembly films on carbon fiber surface via the formation of S-Ag bond.The interfacial bonding strengths of modified carbon fiber/epoxy composites were improved.The relationship between the structures of interfacial regions and properties of the micro-composites was revealed.

Fabrication of Porous C/SiC Composite by Prefabricating Pore Media Technology and Study of Its Property

JI Hong-liang, ZHANG Chang-rui, CAO Ying-bin

2008, 28(1): 82-86.

[Abstract](1144) [PDF 711KB](237)

Abstract:
The porous C/SiC composies was prepared by prefabricating pore media technology that adopt glass fiber as pore media,and its property was studied.The results showed that the technology can control the open porosity and the pore structure successfully by the volume content and distribution of glass fiber in the braids.The porous C/SiC composites have good mechanical properties and good infiltration property.

Experimental Behaviour of Composite Laminates Containing a Hole

ZHU Xi-ping, HAN Xiao-ping, YUE Zhu-feng

2008, 28(1): 87-92.

[Abstract](1208) [PDF 731KB](272)

Abstract:
Experiment studies were carried out on the effect of stitching reinforcement for composite laminates containing a circular hole.The effects of stitching parameters,such as stitching needle distance,row spacing,edge distance,single stitching or double stitching,etc.,were compared and analysed.The tensile strength and failure strain were measured for composite laminates containing a circular hole.The strain concentration and strain distribution regularity were investigated analytically and experimentally.By studing failure sections,the reinforcing effect and failure mechanisms were analysed and discussed for stitching on the edge of hole.The experimental results showed a distinct efficiency of stitching reinforcement for composite laminates containing a circular hole and gave a design method about stitching on the edge of hole. From the current work,it is concluded that: stiffness and the failure strength of the composite laminates are somewhat increased.Reinforced by stitching, there exists a notch strengthing effect,which implies that the maximum strain at the hole edge becomes higher.Compared the stisching reinforcement with unstitching,the scope of strain decling is roughly the same,but the level of strain declining obviously increase.There exist a transform point for tensile strain to compressing strain between 0° and 90°,that is εθ at the transform point.The transform point for single stitching is about θ=56°,and for double stitching is about θ=53°.Synthesizing the data and analysis,the single stitching 1 and the double stitching 1 are the better choices for the composite laminates when reinforced by stitching on the hole.

Aluminum Alloy Creep Test and Its Constitutive Modeling

HUANG Shuo, WAN Min, HUANG Lin, CHI Cai-lou, JI Xiu-sheng

2008, 28(1): 93-96.

[Abstract](1415) [PDF 1012KB](618)

Abstract:
Creep age forming technology was developed for manufacturing the large size and complicated shape one-piece panels of the new generation military and civilian large aircraft.In order to study aluminum alloy creep age forming and present aluminum alloy creep constitutive model used in creep age forming FE simulation,7B04 aluminum alloy creep mechanical property was studied by carrying out creep tests under different stress levels at different temperature such as 145℃,155℃ and 165℃.Result shows that temperature,time and stress level have great effects on material creep.A set of creep constitutive equations that can describe the material creep behavior appropriately were proposed in light of the creep experience laws,and the material constants of creep constitutive equation were fitted by method of nonlinear least squares.

2008 Vol. 28, No. 1