航空材料学报

AID INVE STIGATIOIvI OF DIRECTIONALLY SOLIDIFIED SUPERALLOY DZ4

Sun Chuanqi, Li Chi juan, Lin Shuxi, Wu Changxing

1987, 7(1): 1-9.

[Abstract](1225) [PDF 5922KB](78)

Abstract:
In this paper the composition design, properties, structure and effect of solution heat treated of DZ4, a directionally solidified high strengh cast Nickel-base superalloy,has been described.The research results show that alloy DZ4 exhibiets rather high properties.low density and free Hf It also showed excellent castability and low cost.The favorable role of high temperature solu- lion treatment for improving the properties of the alloy should attributed to high volume fraction of finer phases in ll:c microstructure and to absence of (+')eutectic which occur usually in many cast superalloys.Since the (+') eutectic was removed from microstructure the incipient melting temperature increases and T1 reduces，thus the castability of the alloy would be improved effectively.Alloy DZ4 have been tested in some type of engines and producted for aerocngine turbine blades.

INIVESTIGATION ON MICROSTRUCTURES AND HYDROGEN EMBRITTLEMENT BEHAVIOR IN A ULTRA-HIGH STRENGTH STEEL 300M

Ye Wujun, Zhao Zhenye, Yan Minggao

1987, 7(1): 10-17.

[Abstract](1240) [PDF 5845KB](93)

Abstract:
In this paper，the influence of various isothermal treatments on the micro scopIc characteristics and hydrogen embrittlement behavior in a high strength steel 300M is described.It was found that specimens after isothermal treatments exhibited a higher resistance to HIC tha n that of oil-quenched and tempered materials. With suitable amount of hydrogen contents and certain stress level，the hydrogen induced cracks generally initiated at the interfaces of the martensite packets and/or the sub-structures within them. The resistance ability to HIC of these microstructures decreased according to the following sequence; lower bainite，tempered martensite and secondary martensite.The continous film of retained austenite appeared to be markedly beneficial to the resistance to hydrogen cmbrittlcment of the ultra-high strength steel.

STUDY OF THE QUENCH TRANSFORMATION AND THE PHASE CHARACTERISTICS IN A Ti一10V-2Fe-3A1 ALLOY

Zhang Shaoqing, Tao Chunhu

1987, 7(1): 18-23.

[Abstract](1230) [PDF 4356KB](65)

Abstract:
The quench transformation and the characteristics of quenched phases in a Ti-10V-2Fe一3A1 near bcla titanium alloy were studied by means of x-ray diffraction, transmission electron microscopy and optical microscopy. The quenching temperatures were above and below the transus temperature. The phase constitutions of specimens quenched from various solution temperatures were identified and the phase morphologies were examined. In addition.the relationship between phase lattice parameters and quenching temperatures was given for 、 and 'phases.This alloy has a tendency of precipitation of athermal phase and for the phase to be stress induced ' martensite during quenching.Quenching from the temperatures above the transus temperature，the alloy mainly consists of phase，besides，a small amount of 'martensitc and athermal phase are present in the al- loy,Quenching from the temperatures below the transus temperature，the phase appears in the alloy，in add it ion to the phases mentioned above.

A STUDY OF ALTERNATIVE HIGH AND LOW TEMPERATURE FORGING PROCESS IN TITANIUM ALLOYS

Gao Yang, Cao Chunxiao

1987, 7(1): 24-31.

[Abstract](1233) [PDF 6196KB](88)

Abstract:
The effect of forging alloy has been process variables on the structural uniformity of titanium forging investigated. On the basis of the investigation a new process which can efficiently of big titanium alloy forgings has been improve the structure and properties advanced.The process consists of two alternative cycles of and + work.Ingot was forged in field,then a suitable deformation was carried out in the + field.After that an operation of working or heating was followed.and the final forging was conducted in the + field.This process is called Alternative High and Low Temperature Forging Process(AHLT process). The main principles of the process are that，first，recrystallization of phase and transformation of recrystallized a phase are acted for producing new，fine and uniformgrains;secondly.enough deformation in the + field makes plates change into equia}:ed a.Therefore f finer and more uniform structure can be obtained.

INVESTIGATION OF THE CONTROL OF THE DIREC-TIOIUAL SOLIDIFICATION PARAMETERS AND MICROSTRUCTURE WITH MICROCOMPUTER FOR ALUMINIUM ALLOY

Yin Shiqiao, Mao Xiemin, Shi Zhengxing, Fu Hengzhi

1987, 7(1): 32-37.

[Abstract](1123) [PDF 3533KB](62)

Abstract:
In the paper the microcomputer on一line control of the directional solidifica-tion parameters and microstructure for Al-2.5wt%Cu alloy has been investigat-ed. The test results have shown that the microcomputer on-line control of thedirectional param.aters and microstructure is possible. The test results have alsoshown that of ter the sol idif ication process of Al-2.5wt%Cu alloy has been con-troilcd with microcompuer, th:temperature gradiant ahead of the liquid-sol idinterface tends to become more stable the solidification rate is nearly the givenvalue, the liquid-solid interface more quickly moves towards a stable loca-tion and thE microstructure in the form of directional :!endrite has a high sta-bility.

THE RELATIONSHIP BETWEEN SURFACE STRESS STATE，MICROSTRUCTURE AND HYDROGEN EMBRITTLEMENT FRACTURE OF SUPERHIGH STRENGTH STEEL

Ru Jilai, Wang Renzhi

1987, 7(1): 38-44.

[Abstract](1273) [PDF 4596KB](67)

Abstract:
The surface strengthening effect of shot peening for increasing the resistan- ce to the hydrogen embrittlement of the superhigh strength steel GC4 has been investigated, The role of both surface plastic deformed microstructure and resi- dual stresses for restraining the hydrogen penetration and its diffusion has been discussed. Both caculation of stress field at the notch and the experimental results has shown that the resistance of hydrogen embrittlement of superhigh strength steel GC4 can be effectively increased when the applied stress is below the yield stress of the material.

INVESTIGATION ON THE EFFECTS OF MOISTURE AND TEMPERATURE ON THE GLASS TRANSITION TEMPER ATURE A ND MECHANICAL PROPERTIES OF UNIDIRECTIONAL COMPOSITE MATERIALS

Yang Qiang, Wang Shangen, Fan Tang

1987, 7(1): 45-52.

[Abstract](1336) [PDF 4663KB](72)

Abstract:
In tlhis paper, the glass transition temperatures of Fibrcdux 914 resin and 914C/T300 and T300/5222 unidirectional composites were measured.The hygrother-mal mechanical properties of 914C/T300 unidirectional composite material were analyzed carefully.Chamis' empirical formula for calculating Tg of moisture absorbed resin were discussed.I'hcoric:of Tsai and Chantis on the hydrothermal responses of mechanical properties of unidirectional composite materials were analyzed and compared. On this basis，some formula were modified necessari-ly.The formula selected were checked by the T300/5222 unidirectional composi-te material.The re sults show that the glass transition temperatures of mois- ture absorbed resin could be predicted accurately using modified Chamis' empi-rical Cormula. The results of experiments are in agreement with the results predicted with theories for mechanical properties of unidirectional composite materials.

FIBER REINFORCED COMPOSITES UNDER HYDROTHERMAL CONDITION

Li Zhengwang, Lu Luping, Qin Zhijing

1987, 7(1): 53-59.

[Abstract](1277) [PDF 3607KB](64)

Abstract:
In this paper the fatigue failure criterion proposed and applied to T-T fa- tigue by Hashin-Rotem was extended to T-C fatigue failure at 100℃, wet condi- tion，after water absorbing pretreatment. Through analyzing static strength criterion for accuracy, it was found when the difference between theoretical static strength and experiment value is great, the S-N curve of a laminate can not be predicted by the fatigue failure criterion，while for K-N relation the result is quite satisfactory.

AN ANALYSIS OF TEMPERATURE EFFECT ON LCF CRACK GROWTH RATES INSUPERALLOY GH36

Liu Shaolun, Xie lizhou

1987, 7(1): 60-65.

[Abstract](1180) [PDF 3116KB](63)

Abstract:
The low-cycle fatigue(LCF)crack growth rates of a superalloy ,GH36 have been determined by-D.C.potential drop method in the temperature range from 1600C to 6000C..The experimental results have been analysed by LEFM par-ameter△K and EPFM parameter temperature LCF crack growth rate of alloy GH36 car. be characterized by stress intensity factor range △K,and the coefficient and exponent in Paris' for-mula are function of temperature.An expression for Paris' formula of alloy GH36 over a wide range of temperature has been proposed.da/dN=C(T)(K)n(T)

AN EMPIRICAL METHOD OF PREDICTING CRACK GROWTH LLFE UNDER VARIABLE AMPLITUDE LOADING-FOR ALUMINIUM ALLOYS

Zhang Shijie, Zhu Yigang, Yan Minggao

1987, 7(1): 66-71.

[Abstract](1260) [PDF 2933KB](71)

Abstract:
This paper intends to develop a method of predictin; crack growth life under variable amplitude loading for Aluminium alloys.In the method the ela- slit-plastic compressive boundary in Y-direction created by varying load am-- plitudes was recorded, It is assumed that at every cycle of the .applied vari- able amplitude loading the effect of the variable amplitude history .on the crack opening stress can be replaced by that of an equivalent constant ampli- tude history,both create the same elastic一plastic compressive boundary at the crack tip.The effect of the underloading and the dellycd retardation have been taken into account. The ratios of prediction blocks to test blocks vary from 1.04 to 2063 for 6 kinds of combinations of spectra with different load 1evels. The method should be further improved. It is necessary to'provc the app- lication of this prediction method to other materials.

DETERMINATION OF RESIDUAL STRESS CAUSED BY FORMING IN TRANSPARENT AIRPLANE CA NOPY-AMETHOD USI NG BIREFRI NGE NCEFIRST SLICE BEFORE AND AFTER ANNEALING TO DETERMINE RESIDUAL STRESS

Wang Ziming

1987, 7(1): 72-76.

[Abstract](1168) [PDF 4701KB](60)

Abstract:
In this paper,the author describes a new technique for discriminating therm al stress fringe fro m frozen stress fringe by means of subjecting the first slice to annealing in PMMA and establishes a new photoelastic method for determining quantitatively the residual stress in transparent airplane ca- nopy一一a method using birefringence in first slice before and after anneal- ing to determine residual stress in PMMA the principal points of the method are:thermal stress fringe can be discriminated quantitatively fro m frozen fringe by subjecting the specimen to annealing and calculated the residual stress caused by forming can be calculated according to the thermal stress fringe.The method has been used in engineering.

1987 Vol. 7, No. 1