航空材料学报

CAST SINGLE CRYSTAL NICKEL BASE SUPERALLOY DD3

Chen Dehou, Wu Zhongtang, Zhong Zhengang, Wen Zhongyuan

1983, 3(2): 1-7.

[Abstract](1286) [PDF 4858KB](90)

Abstract:
The absence of grain boundary strengthening elements such as carbon,boron and zirconium,and expensive element tantalum in DD3 alloy elevatesthe incipient melting temperature up to about 1315℃ and reduces the primecost.A solution heat treatment for four hours at 1260士10℃ with air cooling and a aging heat treatment of 32 hours at 870℃ improves markedly composi-tional and structural homogenization of DD3 alloy on a microscale and provides high volume fraction of the fine gamma prime phase.DD3 alloy has excellent balanced level of properties.Its stress rupture property is 19 kg/mm2 higher f or 100 hours at 760℃ and 5kg/mm2 higher at1040℃ than coventionally cast K3 alloy which has similar composition with DD3. DD3 alloy is suitable for production of turbine blade working at 1000℃and turbine vane for 1100℃.

THE FORMATION AND CHANGES OF NEW β GRAINS IN TITANIUM ALLOY TC11

Gao Yang, Zhang Dezhao, Cao Chunxiaoo

1983, 3(2): 8-12.

[Abstract](1192) [PDF 3778KB](60)

Abstract:
This paper describes the formation process and the regular change of new grains in -titanium alloy TC11(Ti-6. 5A1-3.5Mo-1.5Zr-p.3Si).The test results have proved that plastic deformation and subsequentheating in field are two essential conditions for the formation of new grains.If there is only deformation before heating in field，coarse new grains can be obtained; if a certain degree of - defor mation is given after deformation，the uniform and fine new grains can be got.The recrystallization and phase transformation of and in deformed alloy during heating were observed by means of replica electron microscopy;besides, the density，morphology and distribution feature of dislocations underdifferent process conditions were observed using TEM and other methods,These studies have verified that the formation of new grains not onlyresults from recrystallization nucleation and growth of phase， but alsoresults from phase transformation nucleation and growth of recrystallizedand non-recrystallized a grains.

THE MICROSTRUCTURAL CHANGES AND EMBRITTLEMENT OF BT9 TITANIUM ALLOY EXPOSED AT 500℃

Zhang Shaoqing, Li Yaguo, Ge Zhiming

1983, 3(2): 13-19.

[Abstract](1210) [PDF 5450KB](58)

Abstract:
The microstructural changes of BT9 titanium alloy thermally exposed at 500℃ have been investigated by means of optical and electron microscopes,and the effect of different structures and oxygen contents on the thermal exposure embrittlement is set forth.Exposure at 500℃ caused the decomposition of remained phase and the formation of secondary phase.With the prolongation of exposure time，the secondary phase gradually grew up and the new particles of secondury phase precipitated at the same time.The existence of phases in typel and 2 was identified in the regions of decomposed phase.It has been found that the Ti3Al phase precipitated in primary phase after long-term exposure.The precipitation of Ti3Al phase is the main microstructural cause for the ther-mal exposure embrittlement of BT9 alloy.The precipitation of Ti3Al phase is intensified by increasing oxygen content in the alloy, and accordingly the thermal stability of the alloy is reduced.In this paper the thermal stability performance of equiaxed, mixed and lamellar microstructures was compared and the changes of microstructures during thermal exposure were studied. As a result, the eguiaxed microstructure showed the best thermal stability performance, and the lamellar one is the worst in this aspect.

EFFECT OF Mn ON STRUCTURE AND HEAT-RESISTANCE IN A1-CU-RE CAST ALLOY

Cui Guoping, Yu Guifu, Cheng Jianing

1983, 3(2): 20-24.

[Abstract](1178) [PDF 3804KB](52)

Abstract:
This paper conducted an investigation into the effect of Mn on structure and heat-resistance in A1-7Cu-1RE cast alloy with the help of modern metal-physics determining devices.It was found that Mn enhanced grain boundaries due to its formation of intermetallic compounds in combination with other elements, formed the dispersion-distributing secondary phase TMn and restrained the gro wth of themetastable phase 'so as to strength the m atrix and increase the tensile strength without and after exposure of the alloy at elevated temperaturesignif icantly.

INVESTIGATION OF MOISTURE AND TEMPERATURE EFFECTS IN CARBON FIBRE REINFORCED PLASTICS

W ang Shangen

1983, 3(2): 25-33.

[Abstract](1142) [PDF 6197KB](73)

Abstract:
In general composite materials possess high strength and stiffness to weight ratios compared to metals.In recent years composite materials have been developed extensively for use in structural components、A composite material typically consists of a loadcarrying material phase，such as fibres，held together by matrix material.Composite materials exhibit a wide variety of properties depending upon the reinforcement and resin used. Properties of composites are different, when they are subjected to different moisture and temperature conditions. Designermust know the effects of moisture and temperature on the stiffness and strength of unidirectional composites, so as to design a laminate with the desired properties.The objective of this investigation was to evaluate properties of unidi-sectional composites under different moisture and temperature conditions andto calculate strength of cross-ply laminate using S.W. Tsais program.

METALLURGICAL CHARACTERISTICS OF SEAM AND SPOT WELDS FOR THE PRECIPITA-TION-HARDENING SUPERALLOYS

Duan shixun, Sha Yunci, Shi Changjin, Cao Yangchu

1983, 3(2): 34-38.

[Abstract](1184) [PDF 4072KB](50)

Abstract:
In this paper, metallurgical characteristics of seam and spot welds for nickel-base alloy GH99 and nickel-iron-base alloy GH150 were investagated. Experimental results showed that cracks.indications of interface extension，melted grain boundaries and intrusions were easily formed in the welds of the both alloys.The paper explaned the causes and affected factors on the metallurgical defects as well as recommended some technology measures to etiminate or diminish them.

INVESTIGATION OF THE EFFECT OF SOME FACTORS ON FATIGUE THRESHOLD BEHAVIOR IN A HIGH STRENGTH STEEL,30CrMnSiNi₂A

Zhao Wei, Ding Chuanfu, Gu Mingda, Yan Minggao

1983, 3(2): 39-46.

[Abstract](1260) [PDF 6140KB](69)

Abstract:
In this paper the effect of load-shedding sequences，stress ratio ,specimen geometry and crack length on the fatigue threshold behavior in a high strength steel，30CrMnSiNi2A，was investigated. Three load-shedding methods were adopted and discussed. The stress ratio dependence of the fatigue threshold behavior may be primarily ascribed to the occurrence of the crack closure effect.No apparent influence of crack length and specimen thickness on the threshold value for fatigue crack growth was found in the present range of investigation.

APPLICATION OF NEW DETERMINING TECHIQUE TO ORIENTATION DIVERGENCE IN UNIDIREC-TIONALLY SOLIDIFIED COLUMNAR GRAINS

Wang Qingsui, Zhang Guohuan

1983, 3(2): 47-55.

[Abstract](1183) [PDF 5985KB](84)

Abstract:
A method used for determination of orientation divergence in columnar grain structure is reported and the samples of superalloy DZ-22，which are obtained in several directional solidification rates (DSR)，are measured. It is shown that the method is feasible and that reference shall be provided by the results obtained for selecting rational DSR when columnar grain superalloy DZ-22 parts are produced by unidirectionally solidified casting.In the last part，the experimental errors was discussed.

FATIGUE LIFE UNDER COMBINED VIBRATIONS AND LOW CYCLE LOADING

Tu Bailin

1983, 3(2): 56-67.

[Abstract](1146) [PDF 8287KB](39)

Abstract:
In this paper，some experimental studies developing of the crack formation and growth under low amplitude vibrations superiposed on low cycle loading as well as these loading condition the effect on LCF life was reviewed，for structural materials of gas turbine and compressor blades and discs. Method of the predicting FCG rates and critical crack length for combined HCF and LCF was also reviewed, for titanium alloy(Ti-6A1-4V).Experi-mental results show that once the vibrations cycles having on amplitude ratio of 0.2 become active the complex damage is predominantly caused by the vibra-tions cycles.Consequently，predicted FCG rates are to a large extent inde-pendent of the method of assessing LCF damage.

THE IMPROVEMENT OF DUCTILITY AND FRACTURE TOUGHNESS IN Li-CONTAINING ALUMINUM ALLOYS

Feng Weixi

1983, 3(2): 68-74.

[Abstract](1211) [PDF 5122KB](65)

Abstract:
A survey of the developement in aluminum-lithium system which could be used to reduce the weight of airframes was made.This paper briefly descri-bes recent progress on identifying the lower ductility and fracture toughness problems in A1一Li alloys.A part of experimental results on the improvement of ductility and toughness in A1-Cu-Li alloys was also introduced.

THE NATURE OF THE FROZEN FRINGES AND THE RELATIONSHIP BETWEEN THE FROZEN FRINGES AND THE RESIDUAL STRESSES IN POLYMETHYLMETHACRYLATE

Wang Ziming

1983, 3(2): 75-78.

[Abstract](1138) [PDF 15119KB](44)

Abstract:

1983 Vol. 3, No. 2