航空材料学报

Study on Structure and Properties of La_0.9Ba_0.1MnO_3-δ Film

LV Xiao-gong, LIU Jian, DONG Su-yalatu, JIN Yong-jun

2009, 29(5): 1-6.

[Abstract](1245) [PDF 1323KB](228)

Abstract:
A series of thin film which were deposited on Si(100) single crystal substrate by the RF magnetron sputtering were annealing at different temperature.X-ray diffraction(XRD),scanning tunnlling microscope(STM),X-ray photoelectron spectroscopy(XPS),and four prob method were respectively used to measure the phase structures,the morphologies,surface state and magnetoresistance.The study results show the grains of LBMO films annealed in range of 800～850℃ have an epitaxial relationship with Si(100) substrate.The measuring results show that different annealing temperature lead to the quantity of oxygen changing in thin film.Magnetoresistance of the thin film which are annealed at 850℃ arrive at about 30% when the temperatue reach 300K and the magnetic field reach 1.5T.

Microstructure of As-Deposited Ni-Cr-Al Alloy Thin Sheet by EBPVD

GUAN Chun-long, SHAN Ying-chun, HE Xiao-dong

2009, 29(5): 7-10.

[Abstract](1143) [PDF 394KB](254)

Abstract:
Ni-Cr-Al alloy thin sheet with 0.2mm in thickness was deposited on a stainless substrate with 700℃ from a target of Ni-Cr-Al alloy by EB-PVD,and then was removed from the substrate.The thin sheet was characterized by scanning electronic microscopy(SEM),X-ray diffraction(XRD),atomic force microscopy(AFM) and transmission electron microscopy(TEM).It is found that the alloy consists of a two layer structure with different pattern along cross-section direction.Columnar crystals are formed on the substrate side,exhibiting a strong {111} texture,while the equiaxed crystals are dominant on the evaporation side with no textures.Fine and uniform crystals,growing island-likely,are observed on the surface of the as-deposited alloy sheet,and each island consists of a lot of columnar crystals with about 100nm size.A high density of twins is visible within the grains.

Influence of Ceria Content on Performance of Neodymium-Cerium Composite Oxide Thermal Barrier Coatings

ZHONG Xing-hua, XU Zhen-hua, ZHANG Yan-fei, ZHANG Jiang-feng, CHEN Xiao-long, CAO Xue-qiang

2009, 29(5): 11-18.

[Abstract](1193) [PDF 2014KB](239)

Abstract:
Nd2CexO3+2x(x=2.0,2.25,2.5,2.75,3.0) composite oxides were prepared by solid-state reaction and their coatings were fabricated by atmospheric plasma-spraying on the superalloy substrates.The XRD results indicated that Nd2CexO3+2x and their coatings are crystallized in fluorite structure.The influence of CeO2 content on the mechanical properties,i.e.,Young’s modulus,Vickers hardness and fracture toughness of Nd2CexO3+2x,and the thermal shock behaviors of the plasma-sprayed Nd2CexO3+2x coatings at 1250℃ were systematically investigated.With the increase of CeO2 content,Young’s modulus of Nd2CexO3+2x decreases,while Vickers hardness and fracture toughness increase.Near-stoichiometric Nd2Ce2O7 coatings are achieved by the addition of excess CeO2 into the starting powders,therefore the thermal shock behaviors of Nd2CexO3+2x coatings are improved and the thermal cycling lives of the coatings exceed 1000 cycles.The failure of Nd2CexO3+2x coatings is believed to be induced predominantly by the thermal expansion mismatch stress between the ceramic top coat and the substrate/bond coat,oxidation of bond coat and sintering of the ceramic top coat.

Effects of Cold Crucible Directional Solidification Parameters on Macro-structures of Ti-46Al-0.5Si-0.5W Billets

LUO Liang, DING Hong-sheng

2009, 29(5): 19-23.

[Abstract](1149) [PDF 1036KB](227)

Abstract:
A composition of Ti-46Al-0.5Si-0.5W was prepared with directional and fine grains in slab shape.The effects of technical parameters on the grain modalities are studied with orthogonal experiments.The results show that with increasing power grains trends to grow up while the direction of grains is improved.Grains trend to be finer but the direction is more deviated from the growth direction in some extension with increasing withdrawal velocity.When the preheating time is prolonged,the size and the direction of grains both trend to be disbennifit.All of the best directional structures are obtained with withdrawal velocity 1.0mm/min for different crucibles and compositions.

Electrochemical Corrosion Behavior of Friction Stir Welding Dissimilar Weld of 5083 and 6082 Aluminum Alloy

SHEN Chang-bin, ZHAO Ya-dong, LIU Shu-hua, GE Ji-ping, HUANG Zhen-hui, DONG Chun-lin

2009, 29(5): 24-28.

[Abstract](1245) [PDF 967KB](502)

Abstract:
Firstly,the microstructure of the FSW dissimilar weld is characterized by its much finer grains as contrast with the grains of two parent materials.Then,in the ambient temperature 0.2M NaHSO3 and 0.6M NaCl solution,by static weight loss experiment(gravimetric test) and potentiodynamic polarization curve and electrochemical impedance spectroscopy(EIS),the electrochemical corrosion behaviors of friction stir welding(FSW) dissimilar weld of 5083 and 6082 aluminum alloy and two parent materials were comparatively investigated.At the tool rotation rate of 800 r/min,the traverse speed of 160 mm/min and 3 tool tilt,the corrosion potentials of the dissimilar weld were more positive than those of two parent materials,meanwhile,the corrosion rate and the corrosion current density were less than those of two parent materials,Rp(polarization resistance) of the FSW weld was larger than that of the two parent materials.Scanning electron microscope(SEM) observation showed that a few shallow pits presented on the surface of the dissimilar weld,however,a large number of deeper pits emerged on the surfaces of two parent materials.

Effect of Accumulation of Friction Stir Processing on Microstructure and Properties of Cast Pure Aluminum L2

WANG Kuai-she, GUO Wei, WANG Wen, WANG Wen-li

2009, 29(5): 29-32.

[Abstract](1178) [PDF 538KB](225)

Abstract:
Single pass,2-pass and 3-pass of friction stir processing(FSP) were conducted on cast pure aluminum L2.Effect of FSP times on microstructure and properties of cast pure aluminum L2 was studied.The results show that intense plastic deformation results in significant breakup of the coarse dendrites and creates a fine,uniform recrystallized microstructure;accumulative processing times have a little effect on the size of recrystallized grain.The highest microhardness,ultimate tensile strength and elongation increase by 17 HV,39 MPa and 22%,respectively after accumulation of FSP;the surface fracture of the FSPed tensile specimens exhibit a typical ductile dimple-fracture.The differences of microhardness,ultimate tensile strength and elongation between adjacent passes are reduced with more accumulative processing times.

Investigation of Homogenization Treatment on New Al-Zn-Mg-Cu Aluminum Alloy

GONG Peng, ZHANG Kun, DAI Sheng-long

2009, 29(5): 33-38.

[Abstract](1368) [PDF 991KB](490)

Abstract:
The effect of homogenization treatment on a new Al-Zn-Mg-Cu alloy was studied by tensile test,hardness test,optical microscopy,SEM and TEM to investigate the property.The result point out that the overheat temperature of the new alloy producing by semi-continuous casting is 480℃.With the homogenization temperature increasing,the casting of the microstructure of Non-equilibrium phase gradually dissolved into matrix.When the temperature reached 450℃,the dendritic microstructure disappeared and the solid solution limit of the matrix raised with the homogenization temperature increasing.It would be benefited for the second phase-Al3Zr dispersion on the pretreatment of the homogenization temperature,which restrained the recrystallization and improve the plastic technology.the propitious homogenization treatment of the new alloy is 400~420℃/12h+470℃/36h.

Effects of First Aging Stage for Creep Properties of DD3 Single Crystal Superalloys

LUO Yu-shi, HAN Mei, LI Jia-rong, ZHAO Jin-qian, TANG Ding-zhong

2009, 29(5): 39-43.

[Abstract](1172) [PDF 773KB](197)

Abstract:
According to the results of differential thermal analysis and physicochemical phase analysis to casting and standard heat treatment samples,optimized solution and aging heat treatment regimes designed to improve creep properties of DD3 single crystal superalloys were investigated.Experiments on the heat treatment regimes show a high temperature aging treatment addition can significantly increase the γ′ size and improve its distribution,but γ′ phases will be over-ripening,even grow to rafts when aging temperature in excess of 1080℃.When solution heat treated at 1265℃,with γ′ mass fractions increasing,DD3 alloy exhibits best creep rupture and tensile properties.The studies on microstructures and mechanical properties have clarified that the new heat treatment with a first high temperature aging addition resulted in optimized microstructure and remarkably improved creep properties at 760~1038℃.As a result that the new heat treatment: 1265℃/4h,AC+1060℃/4h,AC+870℃/32h were designed.

Formula Optimization Study of Environmental-Friendly Anodized Electrolyte for Magnesium Alloys and Evaluation of Film Performance

GUO Xing-hua, AN Mao-zhong, YANG Pei-xia, LI Hai-xian

2009, 29(5): 44-50.

[Abstract](1178) [PDF 1616KB](337)

Abstract:
Anodized film coated on AZ31B magnesium alloy was prepared under a constant current density in an environmental-friendly electrolyte consisting of potassium hydrate and sodium silicate as the basic electrolyte,sodium borate as the auxiliary filmogen and sodium carbonate as the addition agent.The electrolyte solution was optimized by orthogonal experiment and the suitable concentration of the four kinds of stabilizers mentioned were 60g/L,70g/L,60g/L and 30g/L,respectively.Compared with the magnesium substrate,the anodized film prepared in the optimized electrolyte was smooth,compact and anticorrosion by SEM,potentiodynamic polarization curve and EIS;while the composition of the anodized film was consisted of MgO and Mg2SiO4 by EDS and XRD.

Influence of Graphite on Tribological Properties of C/SiC Braking Material from Needled Felt

DONG Ben-xing, XU Yong-dong, CAI Yan-zhi, JIANG Juan, FAN shang-wu, ZHANG Li-tong, CHENG Lai-fei

2009, 29(5): 51-55.

[Abstract](1206) [PDF 1498KB](247)

Abstract:
Carbon/carbon(C/C) composite with graphite filler addition was prepared by single-direction pressure and pyrolysis,and then a low-cost needle-punched carbon fiber reinforced carbon/silicon carbide(C/SiC) braking material was prepared by reaction melt infiltration.The tribological properties and microstructures of the composite were investigated.The results showed that the graphite mainly existed inside the short-cut webs and between the fiber bundles.The average coefficient of friction(COF) and the friction stability coefficient were rised to the maximum of 0.60,0.78 at a brake velocity of 10m/s.The COF curve rised smoothly and stably at high braking speed,and the wear rate as well as the friction surface temperature decreased obviously as the addition of the graphite filler.The friction film which could relieve the direct contact between the friction surfaces was easily formed on the friction surface.As a result,the tribological properties of C/SiC braking material were significantly improved.

Study on Microwave Permittivity and Radar Absorbing Properties of 2D-SiC_f/SiC Composites with Different Carbon Black Filler Contents

LIU Hai-tao, CHENG Hai-feng, WANG Jun, ZHOU Wang, TANG Geng-ping, ZHENG Wen-wei

2009, 29(5): 56-60.

[Abstract](1311) [PDF 454KB](318)

Abstract:
The microwave permittivity and radar absorbing properties of 2D-SiCf/SiC composites with black carbon filler prepared by precursor infiltration and pyrolysis(PIP) process were investigated.The results show that the KD-I SiC fiber can not be used in radar absorbing materials directly because of the outside carbon coating of SiC fiber,so the carbon coating must be removed by heat treatment process in air.The microwave permittivity of 2D-SiCf/SiC composites with different carbon black contents were measured,and the results show that the permittivity of composites increases obviously with the increase of carbon black filler contents,but owing to the high specific surface area of carbon black and the limit of the viscosity of precursor solution,the maximal volume contents of carbon black in composites are about 7%~8%,which results in the permittivity can not reach a higher value,and the dielectric loss of the composite is below 0.3.The reflectivity of composites with different carbon black contents were calculated,and the results indicate that the absorbing properties of single layer composites are better only within a narrow waveband,which is due to the poor dispersion effect of the permittivity.However,The absorbing properties may be improved by laminated composites with different absorbent contents between layers.

Preparation and Performance Study of Polyfluorin Thin Film by Radio Frequency Magnetron Sputtering Method

GAO Yuan, QIN Xiao-gang, GUO Yun, LIU Hui-tao

2009, 29(5): 61-65.

[Abstract](1179) [PDF 938KB](232)

Abstract:
The preparation technics of polyfluorin thin film on the surface of TR groupware of antenna system of satellite phased array radar is investigated.Polyfluorin thin film is successfully prepared using radio frequency magnetron sputtering method on the surface of TR groupware.The results of electron multipacting effect threshold experiments show that the polyfluorin thin film not only has good insulation capability but also possesses lower secondary electron emission yield,and the electron multipacting effect threshold is improved.XPS and SEM results show that the thin film keeps the property of polyfluorin material well and its uniformity and compactness is capable for practical application.

Preform Design of TC4 Alloy Blade Based on 3D Electrostatic Fields

CAI Jun, LI Fu-guo, ZHANG Peng

2009, 29(5): 66-71.

[Abstract](1247) [PDF 989KB](210)

Abstract:
Based on the 3-D electrostatic fields,a new method of preform design was brought forward by the example of TC4 alloy blade.According to the similarity between the blank flow law and the isopotential line of the electrostatic field,the appropriate shape of the preform was obtained though selecting suitable equipotential line by simulation of 3D electrostatic field.Compared with preform based on the conventional method,the isothermal forging of TC4 alloy blade was simulated.The simulation results showed better forming effect of TC4 alloy blade was achieved by using the preform based on 3-D electrostatic fields.This method is especially suitable for preform design of bulk forming process of forging with complex surface morphology.

Influuence of Processing Methods on Cure Behavior of 5428VB Bismaleimide Resin for Vacuum Bag Curable Composite

ZHANG Bao-yan, ZHOU Zheng-gang, YU Qiang, LI Bin-tai

2009, 29(5): 72-76.

[Abstract](1199) [PDF 878KB](187)

Abstract:
Slurry mixing process was used here to prepare 5428VB bismaleimide(BMI) resin which is suitable for vacuum bag curable composite matrix.The cure kinetic equation and viscosity-temperature behavior etc.of prepared 5428VB resin were investigated and compared to the resin from traditional hot melt mixing process.Results indicated that the 5428VB BMI resin prepared from slurry mixing process and hot melt mixing process had similar cure kinetic parameters,such as the total reaction grade and reaction activation energy,the change of resin processing methods had no influence on the cure reaction process of 5428VB resin;5428VB resin prepared from slurry mixing process had excellent stickiness and 3 months storage life while the resin from hot melt process had no stickiness and only 30 days room storage life,and the resin castings from different processing methods had very similar mechanical properties and glass transition temperatures.

Effect on PTFE Surface Property Treated by Low Temperature Plasma

WANG Yun-ying, MENG Jiang-yan, WANG Yun-ping

2009, 29(5): 77-81.

[Abstract](1268) [PDF 395KB](371)

Abstract:
PTFE films were treated by low temperature plasma,the treatment media was He or O2.The contact angle and the surface energy were investigated by the contact angle instrument and the morphology of PTFE is measured by atom force microscope(AFM) and environmental scanning electron microscope(ESEM).It was confirmed that the contact angle of PTFE decreased and its surface energy increased after it was treated,their water contact angles were from 108°to 80.6°and the surface energy from 24.0 mJ/m2 to 34.4 mJ/m2 after treated by gas He;and the water contact angle were from 108° to 82.4°,the surface energy was from 24.0 mJ/m2 to 35.8 mJ/m2 after treated by O2.It was showed that PTFE surface become more rough and some oxygen-containing active groups were formed after they were treated.In addition,O2 as the treatment media and power is 300 W,modification effect is more better.

Bending Properties and Failure Mechanism of Three Dimensional T300/Epoxy Braided Composites

LI Dian-sen, LU Zi-xing, Li Jia-lu, CHEN Li

2009, 29(5): 82-87.

[Abstract](1245) [PDF 1333KB](376)

Abstract:
The three-point bending tests were preformed on the three dimensional T300/Epoxy braided composites with different braiding angle,fiber volume fraction and braiding structure.The principal bending properties of the composites were obtained and the influences of the braiding process parameters on the bending properties were also analyzed.Macro-Fracture morphology and the scanning electron microscope(SEM) were observed in order to understand the deformation and the failure mechanism of the composites.The results show that the bending loading-flexibility curves of the three dimensional T300/Epoxy braided composites exhibit the linear characteristics.The braiding angle,the fiber volume fraction and the braiding structure were the important parameters affecting on the bending properties of the composites.Moreover,the failure mechanisms of the composites have some correlations with the braiding process parameters.These results can provide an experimental basis for the structural design of the 3D braided composites.

Mathematics Model of Fiber Critical Aspect Ratio of Short-Fiber-Reinforced Elastomer Matrix Composites with Viscoelastic Interphase

ZHU Da-sheng, GU Bo-qin, CHEN Ye

2009, 29(5): 88-93.

[Abstract](1184) [PDF 450KB](244)

Abstract:
A Mathematics model of the fiber critical aspect ratio of short-fiber-reinforced elastomer m matrix composites with viscoelastic interphase was established,and expressions of the fiber critical aspect ratio at the initial time and long time were obtained under different failure modes of interphase.Moreover,the influence of some parameters on the fiber critical aspect ratio were discussed,such as interphase shear strength,interphase shear stress relaxation parameter and interphase thickness.Research indicates that the fiber critical aspect ratio is related to the time,and it reaches to the maximum at initial time and becomes the minimum at long time.The expressions of the fiber critical aspect ratio under three different failure modes of interphase are different.The fiber critical aspect ratio depends largely on the parameters of mechanical properties and structures,it decreases with the increases of the interphase shear strength and thickness,and it increases with the increase of the fiber volume fraction,fiber fracture strength,fiber elasticity modulus and the interphase shear stress relaxation parameter.The fiber critical aspect ratio is quiet different with the variation of interphase thickness.The proposed model is not only suitable for the composite with viscoelastic interphase,but also suitable for the composite with thin-thickness interphase or fiber without surface treatment.

Effect of Fatigue Damage on Distribution of Cracks in 3D C/SiC Composites

ZHANG Jun, LUAN Xin-gang, ZHANG Li-Tong

2009, 29(5): 94-98.

[Abstract](1217) [PDF 854KB](194)

Abstract:
χ2 goodness-of-fit test was introduced to investigate the distribution of the cracks on the matrix and the coating of 3D C/SiC composites before and after fatigue testing.The results show that the crack spacing of the matrix and the coating in the as-received composites obey the normal distribution N(143.75,56.782) and N(562.59,100.092),respectively.After fatigue testing,the crack spacing of the matrix and the coating obey the normal distribution N(105.48,29.162) and N(227.89,25.232)),respectively.The distribution regularities are determined by the three dimensional braided structure of the composites.More cracks are brought in the matrix and the coating due to the fatigue stress,but the character of normal distribution is unchanged.

2009 Vol. 29, No. 5