航空材料学报

TEM observation of precipitates in a 7050 alloy after RRA treatment

GU Yi-jie, LI Yong-Xia, ZHANG Yong-gang, HUANG Zheng, CHEN Chang-qi

2000, 20(4): 1-7.

[Abstract](1667) [PDF 642KB](469)

Abstract:
7050 alloy precipitation aging behavior has been studied by transmission electron microscopy and Vickers hardness tester after retrogression and reaging(RRA) treatment. The RRA behavior was affected by the retrogression temperature. When the retrogression temperature was at 453K and 473K, the retrogression curve can be dealt with in three stages and the RRA treatment can be simply considered as a two step aging process. The result of TEM showed that the dissolve of GP zone caused the decrease of hardness and the precipitation of η and η′ caused the increase of hardness. When the regression temperature was 493K, the hardness decreased, and no hardness valley and peak was not observed on the retrogression curve and RRA curve. Analysis indicated that the three stages of dissolve of GP zone, precipitation of η and η′ and growth of η and η′ can not be distinguished at the retrogression curve because of higher retrogression temperature.

Influence of trace Sc addition on mechanical properties and microstructure of TiAl base alloy

JIN Tou-nan, YIN Zhi-min, LI Dou-xing

2000, 20(4): 8-13.

[Abstract](1628) [PDF 458KB](295)

Abstract:
The influence of trace Sc addition on the mechanical properties and the microstructure of TiAl base alloy were investigated. It is shown that the ambient fracture strength and the maximum deflection of the alloy decreased with the increase of Sc content. However trace Sc addition remarkably improve the high temperature yield strength of the alloy. Introducing of Sc to TiAl alloy leads to forming of a large amount of (Sc,Ti)3Al phase particles, a newly found phase which distribute preferentially near the α2/γ and γ/γT interfaces. The obstacle to inter-lamellar sliding due to (Sc,Ti)3Al particles may be the main cause of the increase of high temperature strength of the alloy.

Investigation of directionally solidified alloy DZ125

CHEN Rong-zhang, SHE Li, ZHANG Hong-wei, WANG Luo-bao

2000, 20(4): 14-19.

[Abstract](1834) [PDF 229KB](527)

Abstract:
DZ125 superalloy for DS thin-wall hollow blades of advanced aero-engines has been developed. It possesses high strength and strength and ductility comparable with the commercially other typical DS alloy such as PWA1422, CM247LC, DZ22 and DZ4. Also the alloy has excellent DS castability and less thin-wall effect. The alloy has been used for producing complex DS blades of a aero-engine and carrying out engine test.

Influence of holding time on thermal mechanical fatigue behavior of GH4133 superalloy

WANG Jian-guo, WANG Lian-qing, WANG Hong-ying, XU Shi-ping

2000, 20(4): 20-25.

[Abstract](1716) [PDF 263KB](343)

Abstract:
The thermal mechanical fatigue (TMF) tests were performed using a specific waveform applied different holding time at maximum temperature. On the basis of the TMF tests, the influence of holding-time on the behavior and the failure life of the TMF under in-phase (IP) and out-of-phase (OP) conditions were investigated. The test results show that the cyclic softening were observed at the cyclic maximum temperature under both IP and OP condition, but no obvious cyclic softening or cyclic hardening at cyclic minimum temperature. The tests results also show that the longer of the holding-time, the shorter of the in phase TMF failure life of GH4133 superalloy, and no obvious influence of holding time on the out of phase TMF failure life.

Microstructure and properties of joint of H62 brass soldered using tin-lead solder

PAN Hui, SUN Ji-sheng, LIU Xiao-fang

2000, 20(4): 26-29.

[Abstract](1754) [PDF 355KB](341)

Abstract:
The microstructure of joint of H62 brass soldered using HLSn60PbSbA solder and the influences of soldering time on microstructure and properties are studied in this paper. It is observed that the joint consists of lead base solid solution, lead-tin base eutectic, copper base solid solution, cellular and block-shaped chemical compounds. Some plate-shaped chemical compounds occurred when soldering time is up to 120s. And it is found that these plate-shaped chemical compounds can be considered to be the main reason for the decrement of mechanical properties, where the mechanical properties of the joint with the shortest holding time are the best.

A study of melting-casting process of a new type ultra-high strength aluminum alloy

LU Zheng, YANG Shou-jie, JIANG Hai-feng, LU Jian

2000, 20(4): 30-33.

[Abstract](1637) [PDF 277KB](209)

Abstract:
Because it is difficult for the ultra high strength aluminum alloys to continuously cast large ingots, the melting-casting process of a new type ultra high strength aluminum alloy was investigated in this paper. And the important points were placed on controlling impurities, refining grains and adjusting the casting parameters etc. In order to getting qualified large ingots, a new process was developed. As a result, good large ingots such as φ290mm and φ308mm were got with the productivity above 90%.

Study of fractographic retroestimation of fatigue stress amplitude

XIE Ming-li, XI Nian-sheng, TAO Chun-hu

2000, 20(4): 34-40.

[Abstract](1661) [PDF 260KB](285)

Abstract:
Fatigue crack propagation rate experiment on 18Cr2Ni4WA steel at different stress ratios and under different loads has been conducted,paris equation has been obtained by data fitting, fatigue striation width has been obtained through fractographic observation under TEM. Then, fatigue stress amplitude have been retroestimated by substituting striation widths into the obtained Paris equation. The result shows that the fatigue striation width only equals the macro propagation rate over a certain stage, which can be judged by the way of plotting the striation width and the parameter y-πa double logarithmic coordinates S-shaped curve. The relative errors of the retroestimated fatigue stress amplitude are less than 10% by the data spots at this stage, The result also reveals that relative errors of the retroestimated fatigue stress amplitude are not sensitive to that of the fatigue crack propagation rate.

Bird impact dynamatic response analysis for windshield

ZANG Shu-guang, WU Cun-hao, WANG Ru-yang, MA Juan-rong

2000, 20(4): 41-45.

[Abstract](1591) [PDF 206KB](348)

Abstract:
DYNA3D finite element method was employed in this paper to investigate bird impact on the windshield systemically. With appropriate load, bird impact dynamic response could be calculated by the method of equivalent dynamic load successfully. The largest stress located in the bird impact area. Properties of film influenced windshield resistant ability seriously. As the difference between elastic modulus of glass and film was about 1～2 magnitude, the windshield had only one neutral layer. When the modulus difference was about 3 magnitude, each glass layer of windshield had a neutral layer. Result from the calculation was in accordance with that of experiments, and this method could be carried out to the research of other laminated types windshields.

Wear behavior of TiCp/ZA43 composite under continuously lubricated condition

XIE Xian-qing, ZHANG Di, LIU Jin-shui, CAI Jian-guo

2000, 20(4): 46-51.

[Abstract](1400) [PDF 277KB](261)

Abstract:
TiC/ZA43 composite was fabricated by stirring casting technique. The tribology properties of the composites were studied using a block-on-ring apparatus. Experimental results showed that addition of TiC improves microstructure and wear behavior of ZA43 alloy. The coefficient of friction (μ) decreases with the TiC volume fraction (Vf), and the width of worn groove decreases with Vf increased. The width of worn groove and μ of the composite during wear testing increase with the applied load increasing. TiC/ZA43 composite has smooth worn surface, whereas unreinforced ZA43 alloy shows adhesive wear. During wear process, sub-surface micro-hardness of ZA43 alloy decreases dramatically, where as that of TiC/ZA43 composite changes little.

Effect of hot air aging and hot water aging on impact properties of polycarbonate

ZHAN Mao-sheng, FANG Yi, WANG Ying, FAN Rong-zheng

2000, 20(4): 52-59.

[Abstract](1742) [PDF 340KB](433)

Abstract:
Hot air aging and hot water aging (at 40℃ and 80℃, 0～400h) of notched impact samples of Bayer-PC (3103), Japan-PC (K1300) and Korea-PC (3027U S) have been investigated. The effect of hot air aging and hot water aging of-PCs on the impact strength and fracture surface appearance was studied. The hot air aging and hot water aging mechanism was discussed. The experiment show that before aging, the impact strengths of-PCs are 95kJ/m2, 83kJ/m2, 55kJ/m2. After hot air aging at 40℃ and 80℃, the impact strengths of-PCs were reduced, and the degree of decrease at 80℃ was great, the order after hot air aging (400h) is: Japan-PCKorea-PCBayer-PC, that is to say, the impact strength of Japan-PC is the best. The influence of hot water aging at 40℃ on the impact strengths of-PCs is the least. The impact strengths of-PCs were reduced after hot water aging at 80℃, the degree of decrease of Korea-PC is the largest, that of Bayer-PC is the least, however, the equilibrium impact strength is same as that of hot air aging. According to SEM photographs of fracture surface appearance, the main fracture mechanism of unaged-PCs is shear yielding,and that of aged-PCs is caving.

2000 Vol. 20, No. 4