航空材料学报

Effect of γ′particle size on tensile and stress-rupture properties for a directionally solidified superalloy

WU Chang-xin, SUN Chuan-qi, LI Qi-juan

2002, 22(3): 1-4.

[Abstract](1306) [PDF 731KB](281)

Abstract:
The effect of cooling rate after high temperature solution treatment on tensile and stress rupture properties of a directionally solidified superalloy was investigated The size of γ′particle in the alloy was increased with the decrease of cooling rate after solution treatment Ultimate strengh and stress-rupture life was increased with the decrease of the size of γ′particle in the alloy while tensile elongation δ% was increased.

Effect of rare earth on mechanism of B-Al permeating

JI Ze-sheng, LI Dong-hua, XIN Ming-de, LI Qing-fen

2002, 22(3): 5-8.

[Abstract](1387) [PDF 251KB](270)

Abstract:
The diffusion models of B atom and Al atom were established, and the effect of rare earth on mechanism of B A1 diffusion was discussed Analysis showed that diffusive rate of B atom was affected by diffusion rate of atom located in front of Fe2B to the matrix and was controlled by the diffusion rate of B atom through crystal cell of Fe2B to the matrix A1 atom was permeated before the surface was covered by compound and was prevented when the surface was completely covered Al formed compounds in the secondary surface The permeation of rare earth increased the number of vacancy and the amount of vacancy body Hence the diffusion rate of B atom was increased and the permeated amount of Al atom was raised.

Preparation of rapidly solidified 1050Al strip by double-belt method

YANG Jin-song, ZHOU Cheng, XIE Jian-xin

2002, 22(3): 9-12.

[Abstract](1446) [PDF 295KB](244)

Abstract:
Al strip with 1mm thickness has been produced directly from the melt through the double-belt rapid solidification process,developed our department The basis principle and characteristics of this method have been described The 1050Al strips with the same thickness have been produced when the cooling belt-velocity is 1m/s and 2m/s respectively, and the finish strips have been examined for metallographic structure It shows obviously that the faster the cooling belt velocity is, the more fine the structure is.

Heat treatment for fine-grain casted K418B superalloy

YU Bao-zheng, TANG Xin, LIU Fa-xin

2002, 22(3): 13-15,21.

[Abstract](1369) [PDF 272KB](247)

Abstract:
The relationship between different heat treatment technical system with the microstructure and the mechanical behavior of fine-grain casted K418B superalloy have been studied It is found that the dimensions of γ′phase as well as the shape and distribution of hypo-carbide at grain boundary have an important influence on the mediums temperature stress rupture properties The suitable vacuum heat treatment technical system has been suggested as 1180℃/2h,AC+930℃/16h,AC for fine-grain casted K418B superalloy.

Investigation on microstructure and properties of recrystallized graphite by Si

QIU Hai-peng, SONG Yong-zhong, Liu Lang, ZHAI Geng-tai, SHI Jing-li

2002, 22(3): 16-21.

[Abstract](1470) [PDF 249KB](411)

Abstract:
The recrystallized graphites were prepared from calcined coke, coal-tar pitch and silicon by the hot-pressing progress in order to investigate the effects of the amounts of silicon on the thermal conductivity, electrical conductivity, bending strength and microstructure of recrystallized graphite Experimental results showed that Si doped recrystallized graphites exhibited higher thermal conductivity and lower electrical resistivity,but lower bending strength than the pure graphite by the same process Compared with pure graphite, the dopant concentration of silicon with 4wt% decreased the electrical resistivity of recrystallized graphite by 25%, but more than 4wt% of dopant silicon hardly changed electrical resistivity of recrystallized graphite For the orientation of graphite layers, the thermal conductivity of RG-Si-6 was 325W/(m·K) at room temperature Microstructural analyses revealed that the degree of graphitization of recrystallized graphite and coherence length of La increased and layers spacing of microcrystalline of d002 decreased with increasing the silicon concentration The degree of graphitization of recrystallized graphite was 94 3% and coherence length of La was 194nm when the amount of dopant silicon was 6wt% in the raw materials XRD analysis indicated that silicon added to the carbon substrate was in the form of α-SiC. The catalytic mechanism of silicon dopant to accelerate the graphitization of carbon substrates coned be explained by the mechanism of decomposition of the carbide.

Application of hot-pressing in C_f/SiC composites Preparing

WANG Jian-fang, CHEN Zhao-hui, ZHENG Wen-wei, XIAO Jia-yu, SUO Jun

2002, 22(3): 22-25.

[Abstract](1446) [PDF 233KB](386)

Abstract:
The effects of hot-pressing in Cf/SiC composites preparing by precursor infiltration pyrolysis (PIP) were studied The results show that hot-pressing can improve the interface between carbon fiber and SiC, increase the density, decrease or even get rid of gaps, and make the material more homogeneous, the properties of Cf/SiC composites are improved and the results repeat well.

Research of a cyanate ester resin matrix suitable for ambient temperature RTM process

LI Wen-feng, LIANG Guo-zheng, YU Qiu-xia, XIN Wen-li, MA Xiao-yan, ZHU Guang-ming

2002, 22(3): 26-29.

[Abstract](1415) [PDF 172KB](311)

Abstract:
Bisphenol A dicyanate ester resin (BADCy) was modified by use of styrene and vinyl styrene The resin matrix found to satisfied with ambient temperature RTM process The cured resin has high thermal stability(HDT:190～200℃) The mechanical performan of the resin is equivalent to 4503A,a modified BMI resin matrix suitable for ambient temperature RTM process The resin matrix has successfully seach the modification demand.

Study of the microcapsule/sol-gel compound coatings

ZHU Li-qun, REN Qiang, CHANG Yan-yan

2002, 22(3): 30-32,37.

[Abstract](1407) [PDF 181KB](249)

Abstract:
Two kinds of microcapsule preparation methods have been studied Though different methods, different component of the microcapsule could be obtained Then the best method has been selected out A kind of microcapsule, which has solid-liquid composite core, it has good preferment in abrasion resistance and corrosion resistance has been attained Through a lot of experiments on solidify process and coat process, a kind of best preparation process of the microcapsule/sol-gel compound coatings has been attained.

The experimental research of impact and CAI of woven composite

ZHENG Hai-yan, LIU Yuan-yong, GUO Wei-guo

2002, 22(3): 33-37.

[Abstract](1403) [PDF 219KB](540)

Abstract:
The current impact experiments have not record the response of force and strain in impact process Elaborate response process of impact for woven composite including impact force of impactor, strain response of different position in the specimen is observed by the special design of impactor and multichannel collection system The compression experiment after impact is discussed in the paper Also, the compression damage force after different impact energy and the strain response of different position are presented It is a satisfying method for experimental research to find the strain distributing in impact and CAI, as well as the compression strength of CAI.

Study on the microstructure of BMI/liquid crystalline epoxy copolymer

CHEN Li-xin, WANG Ru-min, QI Shu-hua, XU Ya-hong, LIAO Jian-wei

2002, 22(3): 38-40,45.

[Abstract](1400) [PDF 215KB](304)

Abstract:
The copolymer microstructure of BMI with liquid crystalline epoxy (PHBHQ) after extending chain was observed Through observation by Scanning Electron Microscope (SEM) showed when BMI:BDAP was equal from 1:1 or 1:1 5 to 1:2, the impact fracture surface was "skin-core" and "impenetrate network"structure respectively The system of BMI/BDAP/PHBHQ was a uniform system analyzed by Dynamic Thermomechanical Analysis (DMTA) During curing the PHBHQ formed oriental ordered mesogenic domain analyzed by Wide-angle X-Ray Diffraction (WAXD) could initiate, branch, terminate the crack dispersed in the copolymer.

Effect of heating method on the microstructure and properties of C/SiC composites

YIN Hong-feng, REN Run, XU Yong-dong, CHENG Lai-fei, ZHANG Li-tong

2002, 22(3): 41-45.

[Abstract](1360) [PDF 296KB](202)

Abstract:
C/SiC composites were fabricated by lower pressure chemical vapor infiltration Effect of two kinds of heating method (electrical resistance heating at 50 Hz and induction heating at 2500Hz) on deposition mechanism of SiC, the densification, microstructure and properties of C/SiC composites was investigated The difference of deposition mechanisms of SiC between the different heating methods was indicated by deposition unit Deposition unit is high temperature molten droplet for electrical resistance heating However it is SiC solid agglomerate for induction heating It is difficult for SiC composites to densify for induction heating because it is difficult for SiC solid agglomerate to infiltrate into fiber bundle But it is easy for high temperature molten droplet to infiltrated into fiber bundle C/SiC composites infiltrated under two kinds of different heating method have different microstructure due to different SiC deposition mechanism This led to C/SiC composites to have higher density,bending strength,fracture toughness and work of fracture for electrical resistance heating as compared with induction heating.

Deposition of ferroelectrics LiNbO₃ films with intense pulsed electron beam ablation

HAN Li-jun, TAN Yi-ping, JIANG Xing-liou

2002, 22(3): 46-49,54.

[Abstract](1288) [PDF 243KB](181)

Abstract:
A new approach of preparation of ferroelectrics LiNbO3 thin film is described The pseudospark electron beams with nanosecond duration can be used for film deposition through the interaction of beam and target to cause rapid melting, vaporization and explosion of target materials, and nucleation and crystallization of ablated target cluster with similar ratio of components occur on the surface of substrates Physical processes of the ablation and deposition of this new technology have been investigated The observation of high resolution electron microscopy, X-ray diffraction, photo-electronic energy spectroscopy have been presented Some experimental results of the preparation of Ferroelectrics LiNbO3 thin film are presented in this paper Experimental results show that such a new approach of film deposition with wide application possesses some unique advantages.

Study on behaviors of continuous glass-fiber reinforced Nylon in corrosive medium

ZHU Ming, LI Ming, ZHOU Wei, DENG Hai-jin

2002, 22(3): 50-54.

[Abstract](1518) [PDF 266KB](264)

Abstract:
In this study, by analyzing weight differences, testing mechanic properties and conducting SEM analyzes, it is found that continuous glass-fiber reinforced Nylon (GF/PA 66) has great oil-proof properties but is strongly damaged by acidic and Alkalescence medium, also, it is slightly affected by the polar medium-acetone.

Preparation of BN matrix composites from borazine polymer precursor pyrolysis

LIU Xiao-guang, LI Guo-jun, TONG Jian-feng, ZHOU Yang, CHEN Da-ming

2002, 22(3): 55-58.

[Abstract](1535) [PDF 198KB](342)

Abstract:
The developments of ceramic matrix composites prepared by borazine polymer precursor pyrolysis have been reviewed Several synthesis methods of pure borazine oligomers were proposed, and experimental principle, preparation process and mechanical properties of fibers reinforced BN matrix composites were introduced in detail.

Control and relief of residual stresses in high-strength aluminum alloy parts for aerospace industry

WANG Qiu-cheng, KE Ying-lin

2002, 22(3): 59-62.

[Abstract](4567) [PDF 183KB](1146)

Abstract:
Residual stresses of a very significant level were introduced when aluminum alloy parts were quenched in cold water from the temperature of solution treatment Residual stresses cause not only distortion and cracking, but also enhance susceptibility to stress corrosion cracking (SCC) and lead to premature failure The aim of this research is how to control and relieve residual stresses in high-strength aluminum alloy parts First, various quenching processes have been evaluated in an attempt to combine low residual stresses with the required levels of mechanical properties during solid solution, involving quenching into boiling water, spray quenching and polymer glycol quenchants The second part of this paper is focused on the comparison of different stress-relieving techniques, highlighting their key attributes, specific advantages and limitations Moreover, the paper concludes that all stress-relieving techniques should be carried out immediately after being quenched in the solution treatment.

2002 Vol. 22, No. 3