航空材料学报

A Study of the Mechanism of Striation Formation and Fatigue Crack Growth in Engineering Alloys

Ouyang Jie, Yan Minggao

1986, 6(1): 1-6.

[Abstract](1204) [PDF 4601KB](71)

Abstract:
A large number of fatigue cracks and fractures of test specimens and components of various engineering alloys were investigated by means of the fractographic technique. It was found that the profile of a fatigue crack appears to be a tunned with numerous steps .In consequence, the striations on the matching surfaces are basically in register other than and kinds of symmetrical conngurations such as peaks to peaks and valleys to valleys. Furthermore, the appearance of the m on surface is usually more regular and distinct than that on the matching surface due to their greater slip length and, sometitaes; slipband notches or Cracks. The process of fatigue crack growth is just like alternatively walking up or down the steps of a path in different areas or grains. A more general and practical model schematically illustrating the mechanism of fatigue crack growth and striation formation, which is one of the most fundamental guestions on fatigue,is proposed.

The Creep Behaviour of a Nickel Base Single Crystal Superalloy

Chen Dehou, Wei Shuyue, Wu Zhongtang, Han Yafang

1986, 6(1): 7-12.

[Abstract](1200) [PDF 4125KB](83)

Abstract:
The creep behaviour of a nickel base single crystal alloy DD3 has been studied in the temperature and stress ranges of 1013 to 1293 K and 176 to 784 MPa, respectively. The Experimental results showed that the creep resistance of DD3 alloy at high temperature up to 1273 K appeared very high compared to current nickel base superalloys and unidirectionall y solidified superalloys, which is attributed to the proper composition and microstructures of present alloy. The results also showed that the creep resistance of DD3 alloy was affected by solution temperature and crystal orientation significantly.

Microstructure Study of Ti-6A1-4V Cast Alloy Refined by Hydrogen Treatmen

Pan Feng, Zhang Shaoqing, Xue Zhixiang

1986, 6(1): 13-19.

[Abstract](1167) [PDF 5358KB](59)

Abstract:
This paper presents the results of an investigation of the influence of hydrogen treatment (hydrogenation-feu tec toid tran s for mation-f dehydrogenation ) on microstructure of Ti-6A1-4V cast alloy, making use of hydrogen as a te mperary alloying element. It was shown by experimental results that after hydrogen treatment the coarse Widmanstatten microstructure of cast titanium alloy was broken up into fine fine + equiaxed microstructure and the grain boundary phase was eliminated. The grain sizes in specimens hydrogen treated are dependent on the hydrogen contents, the eutectoid treatment regime and the dehydrogenation process. In the case of higher eutectoid temprature, the grain size is increased with the increasing of hydrogen content in specimen, but it is decreased when the hydrogen content exceeded a certain value. At lower eutectoid temperatures, the grain size is independent of hydrogen content.The dehydrogenation process also has a significant effect on the grain sizes, a coarser microstructure was obtained under higher temperature and longer duration of dehydrogenation.

Physical Aging Behaviour of a Crylic Sheet ( YE-4 )

Wu Xuanzheng, Lin Dunyi, Shi Weiqi

1986, 6(1): 20-25.

[Abstract](1296) [PDF 3279KB](83)

Abstract:
In tms paper, the influence of both heat treatment and dampness on physical aging for acrylic sheet (YB-4) was studied. During physical aging, the changes of impact strength and physical properties for YB-4 have been investigated. Experiments indicate that aging range of practical interest for YB-4 is between 60 to 125℃ and heat treatment can particular effect Tg and impact strength in this temperature. Heat treatment and dampness are result of the marked drop in Tg and the changes in impact strength for YB-4. Effect of water on YB-4 is physical aging and it is the main factor which effects physical aging for YB-4. In this paper, machanisms that water effects physical aging for YB-4 are discussed. The author considered that effects of water for YB-4 are mainly hydrogen bond separated and cross-linking between micro-moleculars of YB-4 is greatly reduced in this process.

Quantitative Correlation of Mechanical Properties for TC4 Titanium Allpy Die Forging with Microstructural and Forging Technological Parameters

Su Zuwu, Liang Xuefeng, Fu Zuoyi Zhang, Rongshun

1986, 6(1): 26-34.

[Abstract](1193) [PDF 5771KB](88)

Abstract:
The purpose of this paper is to build up a quantitative correlation of tensile properties with microstructural and forging technological para meters for TC4 (Ti-6A1-4V) alloy large die forgings. The results of test and calculation have proved that quantitative correlation of tensile properties (b,0.2,）for TC4 alloy large die forging, with micro-structural and forging technological para meters can be hold by multiple and multinomal regression analysis. The results of analysis of variance have been shown, that multiple and multi no mal regression equations can be applied to estimate tensile properties and chose forging technological para meters of lange die forgingsfor TC4 alloy.

Simulation of Blade Precision Forging Process by Rigid-visco-plastic Finits Element Method

Lian Jianmin, Li Xunti, Li Chenggong

1986, 6(1): 35-42.

[Abstract](1221) [PDF 4484KB](57)

Abstract:
The forging of a blade cross-section is simulated by rigidviscoplastic finite element method ( RVPFEM ) with model lead.Defor mation behaviors of the forging process are discussed, based on the solution.The effects of friction condition and the bridge shape on material flow are investigated. The reason of the shear band appearence in blade forging is analysed.The results show that the simulations by RVPFEM can describe distinctly the whole process of blade forging and provide a lot of information for forging preform design and prediction of defect formation and location .The meshes drawn by computer arc in good agreement with the results of experiments.

An Investigation of Creep Crack Growth Behaviour in GH36 Superalloy

Liu Yan

1986, 6(1): 43-48.

[Abstract](1148) [PDF 3354KB](77)

Abstract:
Creep crack growth experiments were conducted on GH36 superalloy, using both CT and SENT specimens. The fracture mechanics parameters, K11,C*,rcf and Cm* were applied to correlate the CCG rate , where C*m is a new parameter proposed recently by author which includes the effects of the elastic strain rates and, especially, those introduced by crack growth. In fact, C*m determines the amplitude of the HRR-field under transient creep conditions. Experimental results indicate that very good correlation exists between crack growth rate a and new parameter C#m# In contrast, the correlation with other parameters is very poor.

Evaluation of the Damage of Carbon/Epoxy Composite Laminates under Static and Fatigue Loading by Thermographic Analyses

Xian Xingjuan, Zheng Weiping, Hu Wenyou

1986, 6(1): 49-56.

[Abstract](1208) [PDF 5343KB](60)

Abstract:
During the process of da mage in composites microstructures under loading, heat is generated and local temperature will rise in the specimen.In this study frared ther mograpnic technique was used to investigate the damage spread of carbon fiber rein forced epoxy laminates of dif ferent layup either with notch (SEN and CHN ) or unnotched, under static or fatigue loading.The degree of damage was evaluated according to the variation of temperature rise，and the damage dimension of the specimen was examined from the isotherms of tem-perature distribution .The dependence of temperature rise on stress level as well as fatigue life was discussed.

The study of LCF Crack Propagation under Controlled Strain Loading

Wang Gengsheng, Xie Jizhou

1986, 6(1): 57-62.

[Abstract](1178) [PDF 3258KB](59)

Abstract:
To deal with typical strain-controlled loading in the regions between blades and disc on the turbine-disc. The LCFP property of the Iron-base superalloy GH36 was studied under controlled displacement fatigue test. Testing data, at 550℃ in air, showed that there exists an obvious difference in a-N relationships between controlled load testing data and that of controlled strain test. Under controlled strain condition, the crack growth rate decreases when the crack becomes long enough. The testing data also were related with parameters K and J. As a result, the J appeared more suitable for the testing data.

The Investigation of Isothermal Transformation of Ti-10V-2Fe-3A1 Titanium Alloy

Lu Ruoying, Zhang Xiaojun

1986, 6(1): 63-68.

[Abstract](1116) [PDF 4075KB](72)

Abstract:

The cold Rollability and Recrystallization upon Annealing of Ti-10V-2Fe-3Al Titanium Alloy

Pan Yaqin, Liang Youming, Pang Lipin, Lui Wei

1986, 6(1): 69-72.

[Abstract](1232) [PDF 2370KB](74)

Abstract:

On the Experimental Study of Fitting Values in X²-test

Su Hansheng

1986, 6(1): 73-77.

[Abstract](1122) [PDF 3421KB](64)

Abstract:

1986 Vol. 6, No. 1