航空材料学报

SOLIDIFICATION STRUCTURES OF Ni-Al-C-Ti (Hf, Nb, Ta) QUATERNARY SUPERALLOYS

Liu Lin, Fu Hengzhi, Shi Zhengxing, Fang Xiaohua

1990, 10(2): 1-6,43.

[Abstract](1429) [PDF 760KB](157)

Abstract:
Directionally solidified techniques were used for a group of Ni-Al-C-Ti(Hf, Nb, Ta)quaternary nickel-based alloys specially designed in this study. By using DTA analysis connecting the metallography observation, it is revealed that the solidification features of these simplified superalloys are similar to industrial superalloys. These kinds of alloys can act as model alloys for studying the soli-dification processes of industrial superalloys. The striking solidification features of the simplified superalloys revealed by quantitative metallurgraphy, electron microprobe and SEM techniques are as follows:(1)The morphological charicter of TiC and HfC is basically the same the less developed arms, relative small size and disconnected block; on the contrary, both NbC and TaC grow in the shape of typical Chinese-script type. This disparity is a basic reason for causing morphological changes of MC carbides in industrial superalloys,(2)There are more amounts ofγ-γ＇eutectics in Ti and Hf bearing alloys than that in Nb and Ta bearing alloys.(3)The dendritic segre-gation of carbide formation elements decresess according to the sequence of Hf, Nb. Ti and Ta.

THE INFLUENCE OF Si CONTENT ON THE MICROSTRUCTURE AND PROPERTIES OF HIGH TEMPERATURE TITANIUM ALLOY (7715C)

Luo Yuexin, Xu Jialong, Chen Kexiu

1990, 10(2): 7-12.

[Abstract](1352) [PDF 822KB](161)

Abstract:
The effects of Si content on the microstructure and machanical properties such as room temperature tensile strength, room temperature tensile strength with notch, 541℃ tensile strength, impact toughness and thermal stability of 7715C alloy have been investigated in this paper. The results show that there exists an optimum Si content of 0.2wt% where the best combination of the above properties is obtained. The relation between Si content and the peak φ value of alloys after a period′s exposure at 540℃ shows that the longer the alloys were exposured, the less Si content corresponds to the peak φ value. Peak φ values are found for 0.3 wt% Si alloy after 100 hours exposured and for 0.2 wt% Si after 200 hours exposured, respectively. Examination of the microstructure illustrates that the optimum Si content is the maximun solution content of Si in the alloy when no Si compounds formed. As more Si compounds precipitate with increasing in Si content and exposure time, the Si content of alloy with peak φ value moves to the left, i.e., less Si content, when the exposuring time is extended.

ENVIRONMENTAL ATMOSPHERE EFFECT ON FRETTING WEAR CHARACTERISTICS OF TITANIUM ALLOY

Xu Yongli, Wang Shihong, Liang Youming, Dong Xianglin

1990, 10(2): 13-20.

[Abstract](1509) [PDF 1337KB](162)

Abstract:
Fretting wear chracteristics of TC11 titanium alloy in argon and air, and its relations with main experimental parameters(such as normal load, amplitude of slip and frequency of vibration)have been studied. Fretting mechanism of TC11-TC11 and TC11-GCr15 friction couples was also discussed with techniques of X-Ray diffraction, energy spectrum, SEM and ion probe. The experimental results showed that fretting wear was aggregated with increasing amplitude and frequency of vibration. Fretting wear process in argon was compossed mainly of two stage, i.e initial adhesion and latter fatigue damage caused by alternative shear stress at the sub-surface of the lmaterial. Meta transfer phenomenon and delamilation plaied a more important role in fretting wear in air for TC11-GCr15 friction couples.

EFFECTS OF CYCLIC STRAIN-RATE METHOD ON THE SUPERPLASTICITY OF Ti-10V-2Fe-3Al ALLOY

Wang Gaochao, Du Zhongquan

1990, 10(2): 21-25,20.

[Abstract](1370) [PDF 427KB](172)

Abstract:
The newly developed cyclic strain-rate method implies that in a superplastic tensile test the strain-rate varies in accordance with a given cyclic regime until the specimen breaks down, obtaining the superplastic mechanical parameters of a certain metallic material. in this paper, this method has been used to investigate the superplastic behaviour of Ti-10V-2Fe-3Al alloy. The test results show that this method, if compared with the constant strain-rate method. can effectively improve the superplastic behavior of this alloy in terms of the higher values of elongaftion and greater strain-rate sensitivity exponent. For example, at the optimal deformation temperature 800℃, the elongation is raised from 296 to 440% and the m-value from 0.36 to 0.48. The cyclic strain-rate method provides a new approach to evaluate the superplastic behaviour of Ti-10V-2Fe-3Al alloy.

EFFECT OF COLD WORKING PRIOR TO AGING ON THE MICROSTRUCTURES IN AN Al-Li-Cu-Mg-Zr ALLOY

Zheng Ziqiao

1990, 10(2): 26-31,37.

[Abstract](1299) [PDF 1398KB](189)

Abstract:
The effect of cold rolling deformation prior to aging on the aging characte-ristics and microstructures in an Al-Li-Cu-Mg-Zr alloy was studied by hardness measurement and electron microscopy. It is found that a small amount of cold rolling deformation encouraged the homogeneous precipitation of S′phase in the matrix and decreased the widths of PFZ. Age hardening was increased by coprecipitation of S′phase together with δ′phase. Formation of the PFZ has been explained by a vacancy depletion and solute depletion mechanism, and the relationship between pre-deformation and microstructure were also discussed.

THE STUDY OF THE STRUCTURE OF THE MANGANESE-CONTAINING DISPERSOID PHASE IN 2024 Al ALLOY

Li Chunzhi, Wang Shuncai, Jin Yan, Yan Minggao

1990, 10(2): 32-37.

[Abstract](1486) [PDF 1590KB](229)

Abstract:
The rod-shaped dispersoid phase in 2024 Al alloy has been studied, using convergent beam electron diffraction(CBD), selected area electron diffraction (SAD)and electron microprobe X-ray analysis. The dispersoid phase has been designated as Al20Cu2Mn3. The structure of the phase has been determined to be B center othorhombic, possessing a Bbmm space group. It was found that the phase easily formed multipletwins and010electron diffraction pattern from the multiple-twins showed ten-fold symmetry.

FEATURE ANALYSIS OF UNDT OF ADHESIVE BOND STRUCTURES

Hu Shaohai, Zhang Shujing, Yuan Zhengming

1990, 10(2): 38-43.

[Abstract](1394) [PDF 425KB](248)

Abstract:
The application of feature analysis of ultrasonic nondestructive testing(UNDT) of adhesive bond structures(ABS)is presented in this paper. Frist, the defects types of ABS and the reasons are analysed. Then, the features of ultrasonic signal in time domain, frequency domain and transfer function domain, which relate to the quality of ABS, are discussed. Features analysis and pattern recognition are applied to classfy the defects type and to estimate the bond strength. Finally, aexample of feature analysis of UNDT to estimate the bond strength is presented in this paper.

CURRENT SITUATION OF DEVELOPMENT OF CARBON FIBER WITH SUPERIOR PROPERTIES AND THEIR MANUFACTURING ENGINEERING

He Fu

1990, 10(2): 44-52.

[Abstract](1299) [PDF 630KB](190)

Abstract:
The situation of development on carbon fibers of polyacrylonitrile series and their manufacturing engineering were described in this paper.

PROGRESS IN RESEARCH OF HIGHTEMPERATURE STRUCTURAL CERAMICS

Jin Zhihao, Wang Xiaotian

1990, 10(2): 53-58.

[Abstract](1307) [PDF 491KB](172)

Abstract:
In this paper the progress in research of high-temperature structural ceramics at recent years is reviewed in detail.

DUCTILITY AND FRACTURE TOUGHNESS IN RSP P/M ALUMINIUM-LITHIUM ALLOYS

Jiao Chengge, Yu Guifu, Han Yafang

1990, 10(2): 59-63.

[Abstract](1463) [PDF 387KB](160)

Abstract:
The problem of ductility and fracture toughness in RSP P/M aluminium-lithium alloys has been reviewed. The developments on improvement of ductility and toughness in RSP P/M aluminium-lithium alloys were briefly described.

1990 Vol. 10, No. 2