航空材料学报

Microstructure and Mechanical Properties of a Mg-9Gd-4Y-0.65Mn Alloy Processed by Thermo-Mechanical Treatment

CHEN Jian-mei, ZHANG Xin-ming, DENG Yun-lai, XIAO Yang, JIANG Hao

2006, 26(2): 1-7.

[Abstract](1379) [PDF 1493KB](330)

Abstract:
Mg-9Gd-4Y-0.65Mn alloy to be investigated was prepared by "fluxes-melting method" and its hot-rolling was carried out.Microstructure evolve rule in the different threat treatment condition and mechanical properties at room temperature and at high temperature of the studied alloy were investigated by means of modern analysis methods.The results showed that the hot-rolled alloy had a high strength from room temperature to 300℃, fine grains of which did not get growth obviously, and good heat stability.A good combination of high strength and high ductility at room temperature was attained for the material hot-rolled and after T6.The processed alloy exhibited superplastic behavior while tensile testing at 400℃.

Simulation of Residual Stress of Reversible Cold-Rolling and Deformation Control Study on Vertical Rolling

ZHAO Li-li, ZHANG Yi-du

2006, 26(2): 8-11.

[Abstract](1423) [PDF 463KB](207)

Abstract:
The residual stresses of aluminum alloy thick-board in the rolling process of bitting, shoot and reversing were simulated by using highly non-liner software Msc.marc ,elas-plastic large deformation finite element method(FEM) and established three-dimensional model.In addition, the difficulties to bite during initial stage of rolling in FEM and to control the deformation due to vertical rolling were solved too.The established three-dimensional model was proved to be effective by comparing the results of FEM simulation and experimentation.The only once rolled stress could be decreased by reversible rolling and the rolled stress on thick direction was M distribution.Dog-bone section deformation due to vertical rolled could be rectified by small press horizontal rolled after vertical rolling to assure the required precision of board.

Effects of Powder Particle Size on Microstructure and Properties of RS P/M Al-Fe-Mo-Si/Zn-Al Composites

LI Wei, LI Pei-yong

2006, 26(2): 12-15.

[Abstract](1449) [PDF 676KB](206)

Abstract:
The microstructure, tensile properties and damping capacity of Al-9.0Fe-1.8Mo-l.7Si/5.0%(Zn-30% Al) metal/metal composites with different powder particle size were investigated.The powders were produced by gas-atomization.The powders with average size(d50) of 27.3 ,36.2,41.6μm were canned and degassed, followed by hot extrusion.The results showed that the coarser powders were, the larger dispersoids were.In addition, the agglomeration of the dispersoids could be found in the coarse powder.The strength of the material with coarser powders was lower than that of fine powders.The material with finer powders exhibited better damping capacity at room temperature, while that with coarser powders possessed better damping capacity above 100℃.

Effects of Rare Earth on Growth of Voids along Interface between Al₂O₃ and Aluminizing Layer

ZHANG Wei, FAN Zhi-kang, GUO Xian-jun, WEN Jiu-ba, ZHANG Jin-min

2006, 26(2): 16-19.

[Abstract](1471) [PDF 474KB](258)

Abstract:
The effects of rare earth(RE) elements on the growth of the voids along the interface between Al2O3 and aluminizing layer and the oxidation resistance of aluminized steel were investigated through measuring the variations of the average diameter and depth of interfacial voids with oxidation time, and compared with those of pure aluminized steel.The results show that, the growth rate of average diameter of voids in RE-added aluminized layer is only one half of that in pure aluminized layer and the variations rate of the average depth with the average diameter of interfacial voids is only three-fifths of that in pure aluminized layer, and the number of voids in unit area is less than that of pure aluminized layer too.RE can delay the formation and aggregation of the void and improves oxidation resistance of aluminized steel.The mechanism of the RE effect on the nucleation and the growth of interfacial voids was also discussed.

Study on Corrosion Resistance of Micro-Arc Oxidation Ceramic Coating of High Strength Casting Aluminum Alloy

CUI Shi-hai, HAN Jian-min, LI Wei-jing, XU Xiang-yang, LIU Yuan-fu

2006, 26(2): 20-22.

[Abstract](1517) [PDF 420KB](314)

Abstract:
The influence of thickness of micro-arc oxidation(MAO) coatings on the corrosion resistance of high strength casting aluminum alloy ZL205 was investigated by using salt spray test.It was found that MAO coatings improved the corrosion resistance of ZL205 alloy obviously.The corrosion resistance of MAO coatings increased with the increase of coating thickness.When the coating thickness was thicker than 30μm, the corrosion resistance of PEO coating increased only a little with the increase of PEO coating thickness.Results of SEM and XRD showed that surface morphologies and phase composition of MAO coatings altered with the increase of oxidation time, which resulted in different corrosion resistance of MAO coating.

A Study of Preparation of Protecting Coating on SiC Filaments by CVD Process

CAI Shan, LI Zhan-yi, DONG Yan, YAN Ming-gao

2006, 26(2): 23-28.

[Abstract](1406) [PDF 657KB](285)

Abstract:
The coating of SiC filament prepared by CVD process was investigated.Test indicated that dense B4C protective layer about 2~3μm thick could be coated on SiC surface at about 1350℃ by using a gas mixture of H2 + CH4 + BC13 and controlling the filament takeup speed matching the deposition process of SiC.The tensile strength of B4C-coated SiC fibres were basically unchanged in optimal parameter.Meanwhile, dense and smooth B4C-C coating with thickness of 2~3μm was also deposited on SiC surface at 1180-1250℃ by using a gas mixture of CH4 + BC13.The results showed that the binding strength between B4C-C coating and SiC filament was better than that between B4C and SiC.At the same time, the tensile strength of SiC filament with B4C-C coating was increased of about 10% .Test also indicated that B4C or B4C-C coating could prevent the deleterious fiber-Ti matrix interface reaction and the tensile strength of titanium matrix composites reinforced by SiC filaments with B4C or B4C-C coating were significantly improved.

Effect of Pyrolysis Mode of First Cycle on C_f/SiC Composites Fabricated by Precursor Pyrolysis

LI Fan, CHEN Zhao-hui, WANG Song, ZHENG Wen-wei

2006, 26(2): 29-32.

[Abstract](1404) [PDF 628KB](208)

Abstract:
Three-dimensional braided carbon fiber reinforced SiC composites were fabricated via polycarbosilane infiltration and pyrolysis, and the effects of different pyrolysis modes of the first cycle on the matrix and mechanical properties of Cf/SiC composites were investigated.The results show that the precursor has the highest ceramic yields of 67.2% in case of gas-pressure pyrolysis and the pyrolysis modes have little effect on crystal structure of matrix.When the first pyrolysis was conducted under vacuum, the resultant composite showed the highest mechanical properties, 404MPa in flexural strength and 20.2MPa · m1/2 in fracture toughness, which are 1.407 and 1.423 times of those of the composite derived from gas-pressure pyrolysis, respectively.

Study on Preparation of Continuous Si-Fe-C-O Radar-Wave Absorbing Fibers by Precursor Method

CHEN Zhi-yan, WANG Jun, LI Xiao-dong, WANG Ying-de

2006, 26(2): 33-36.

[Abstract](1414) [PDF 421KB](304)

Abstract:
A polyferrocarbosilane(PFCS) was synthesized from polydimethylsilane and ferrocene.Low specific resistance Si-Fe-C-O fiber was prepared with the following process:The PFCS was porose melt-spun, the resulted green fibers bundle were cured by heating in air, and the cured fibers were continuously sintered under an inert atmosphere.The specific resistance of the fiber could be reduced to 10-2Ω · cm, the tensile strength was about 2.0GPa,and the length was more than 500 meters.The structural material composed of the Si-Fe-C-O fibers and epoxy resin exhibited good property of radar-wave absorbing in the range of 8~18GHz.The element Fe contained in the fibers could advance growth of β-SiC crystalline grain, and reduced the specific resistance of Si-Fe-C-O fibers.

Effect of Specific Heat of Thermal Resin on Simulation of Composite Curing Process

YAN Yong, ZHUANG Zhuo, ZHOU Zheng-gang, ZHANG Bao-yan, CHEN Xiang-bao, XING Li-ying

2006, 26(2): 37-40.

[Abstract](1657) [PDF 2333KB](210)

Abstract:
When simulating the curing process of composites, the specific heat of cured resin was often used as that of the resin during the whole process.This could cause great error in the simulation result.As the heat release of curing reaction, the specific heat of resin during curing was difficult to be measured.A hypothesis was presented that the specific heat of resin changed greatly at the gel point.Before that point the specific heat of uncured resin was linearly lessening to the value of cured resin, while after gel point the specific heat of cured resin was used.The simulation result was in good agreement with the experiment data.

Study on Chemorheology of Low Temperature Curing LT-01A Epoxy Resin System

LIU Tian-shu, CHEN Xiang-bao, ZHANG Bao-yan, ZHOU Zheng-gang

2006, 26(2): 41-43.

[Abstract](1486) [PDF 235KB](387)

Abstract:
The chemorheology of low temperature curing LT-01A epoxy resin system was investigated using a cone-and-plate rheometer.The chemorheological equations under both isothermal and dynamic curing conditions were established respectively based on Arrhenius 1st order model.By following the temperature procedure of the cure cycle of the resin system, the validity of the chemorheological equations obtained was verified.Results showed that the chemorheological equations obtained could describe the chemorheological behavior during the practical cure process of the resin system accurately.

Study on Performance of PAEK Toughened LP-15 Polyimide Resin System

XIONG Lei, ZHANG Zuo-guang, LI Xiao-gang, LI Hong-yun, YI Xiao-su

2006, 26(2): 44-46,51.

[Abstract](1354) [PDF 450KB](188)

Abstract:
The high performance thermal plastic polymer PAEK was used to toughen LP-15 polyimide.The performance of polyimide containing different PAEK concentration was studied.The results indicated that the impact strength and flexural strength were improved remarkably by blending of two components, while the glass transition temperature of the neat resin did not change much.In addition, the impact property of LP-15/PAEK composite was improved obviously.

Study of Approaches to Modifying Polymeric Materials for Better Compatibility with Liquid Oxygen

WANG Ge, ZENG Jing-cheng, LI Xiao-dong, LI Gong-yi, TANG Yun

2006, 26(2): 47-51.

[Abstract](1536) [PDF 416KB](187)

Abstract:
Epoxy and cyanate ester co-curing systems were selected as the main system of the study.Their compatibility with liquid oxygen was characterized by the liquid oxygen impact test.Thermal analysis and oxygen index were used to represent the polymers' anti-oxidation and flame-retardant properties.The inherent relationship between anti-oxidation and flame-retardant properties of polymers and their compatibility with liquid oxygen were studied thoroughly.The conclusion was drawn that polymers with better anti-oxidation and flame-retardant properties had better compatibility with liquid oxygen.Two co-curing system with desirable compatibility with liquid oxygen were established by modifying the polymers in the two ways respectively.

Study of Properties of Silicon Carbide Fiber Reinfoced Si-O-C Composites Using Low Cost Polysiloxane

FAN Zhen-xiang, CHENG Hai-feng, ZHANG Chang-rui, TANG Geng-ping, CHU Zeng-yong, WANG Jun

2006, 26(2): 52-56.

[Abstract](1470) [PDF 574KB](226)

Abstract:
Silicon carbide fiber reinforced siliconoxycarbide(Si-O-C) composites were fabricated via precursor infiltration and pyrolysis using polysiloxane.Flexural strength, tensile strengths, shear strength, dentsity, thermal expansion coefficient, thermal conduction coefficient, ablative properties of SiCf/Si-O-C composites were tested .The results indicated that SiCf/Si-O-C composites had fairly excellent properties.Microstructure and properties of SiCf/Si-O-C composites was discussed, the high properties were mainly attributed to ideal interface structure and density.

Study on Electric Heating Property of Carbon/Ceramic Composites

LI Yan, XIA Jin-tong, SHAO Hao-ming, LU Xue-feng

2006, 26(2): 57-61.

[Abstract](1364) [PDF 540KB](289)

Abstract:
Carbon/ceramic composites were prepared by ball milling of the matrix ceramic material(kaolin) and the conductive components(graphite and carbon black), die forming and sintering processes.The phase composition, microstructure and electric heating property were analyzed and tested using XRD, SEM and numerical thermoscope, etc.The results show that:1) reactions are not supposed to take place between the matrix ceramic material and the carbon conductive components at the specific sintering conditions, therefore, the conductivity of the carbon materials won't be weakened;2) continuous conducting passages are formed inside the carbon/ceramic composites with the contents of graphite, carbon black and both graphite and carbon black(mgraphite:mcarbon black=1:1) being 30, 25, 30wt% respectively, which resulting in a good electric heating property of the composites.

Study of Using Free-Space Method for Measuring Complex Permittivity

LU Zi-yan, TANG Zong-xi, ZHANG Biao

2006, 26(2): 62-66.

[Abstract](1632) [PDF 392KB](448)

Abstract:
The characteristic of electromagnetic wave through the dielectric planar sample in free-space was analyzed.The relations between the scatter parameters and the complex permittivity were found, and three expressions were obtained to determine the complex permittivity.The error analysis of these three expressions was performed.By combining these three expressions, instability problem and phase-shift ambiguity problem of thick samples were solved.The test system was established and several samples were measured at X-band.The validity of the method and test system was proved by experiments.

A Morphological Study Based Ultrasonic Attenuation Model of Carbon Fiber Reinforced Plastics Porosity Testing

LIU Ji-zhong, JIANG Zhi-feng, HUA Zhi-heng

2006, 26(2): 67-71.

[Abstract](1403) [PDF 590KB](326)

Abstract:
A morphological study of voids and a statistical study of the voids' morphological features in carbon fiber reinforced plastics(CFRP) were implemented using microscopy and image analyzing system.The results show the voids morphological features are correlated with the CFRP porosity and the fraction of voids is nearly a logarithmic normal distribution with the voids' size.Based on the study, an ultrasonic attenuation model of CFRP porosity testing was established in which the voids' statistical and morphological features were considered.

Alloying Design of Titanium Aluminum Intermetallics and Research Progress

LI Bao-hui, KONG Fan-tao, CHEN Yu-yong, CHEN Zi-yong, ZHANG Jun-wei

2006, 26(2): 72-78.

[Abstract](1710) [PDF 605KB](555)

Abstract:
The effects of alloying elements on crystal structure, microstructure and properties of TiAl alloys were analyzed.β phase was introduced at elevated temperature to improve the hot-workability by adding high alloying element(like high Nb, V, Cr, Mn).A small amount of additions(like C, B, rare earth) improved the properties of TiAl alloys through the effects of refinement and precipitations.Favorite microstructures could be obtained by various new approaches of heat treatment and thermo-mechanical treatment.Forming technologies and applications of TiAl alloys in recent years were summed up.And the development tendency was prospected.

2006 Vol. 26, No. 2