航空材料学报

INVESTIGATION ON DIRECTIONALLY SOLIDIFIED HIGH-STRENGTH SUPERALLOY DZ22

Chen Rongzhang, Wang Luobao, Wang Yuping

1991, 11(1): 1-11.

[Abstract](1405) [PDF 1306KB](188)

Abstract:
Alloy DZ22 possesses rather high intermediate and elevated temperature strength compared with the advanced commercial DS alloy PWA1422.The alloy compositions are similar to PWA1422 but the content range of Hf,C and Zr was changed through systematic tests.The present melting technology for master alloy ingot and DS process parameters for components are suitable for the alloy.The alloy revert which has been specially processed may be reused.The mould withdraw speed daring directional solidification has strong effects to crystal orientation and alloy structure,hence,to mechanical properties of DS casting.Increment of soulution-treatment temperature may increase obviously longitudinal stress-rupture life at high temperature but decrease transversal one at intermediate temperature.The production practice in batchs has demonstrated that alloy DZ22 has not only high mechanical properties but also excellent process performance including castability,weldability and mechinability.It is indeed a favorable material for advanced aero-and stationary gas turbine engine blades with complex inner cooling passage.

EFFECT OF SOLIDIFICATION RATE ON THE MICROSTRUCTURE AND SOLUTE REDISTRIBUTION OF A SINGLE-CRYSTAL NICKEL-BASE SUPERALLOY

Wang Huaming, Tang Yajun, Zhang Jinghua, Zhang Ziya, Li Yingao, Yu Yang, Hu Zhuangqi

1991, 11(1): 12-18.

[Abstract](1397) [PDF 797KB](249)

Abstract:
The effect of solidification rate on the microstructure and solute redistribution of a newly developed hot corrosion-resistant single-crystal Ni-base superalloy was studied under commercial production conditions.Results show that solidification rate has strong effect on the solidified structure and solute segregation.As solidification rate increases,the primary and secondary dendrite arm spacings decrease markedly,the volume fraction and average dimension of interdendritic microporosity reduce considerably,the solute segregation improves effectively,and the morphology of interdendritic γ/γ' eutectic varies gradually from large packets which are actually the aggregates of coarse primary γ' blocks to nodules of superfine lamellar or screen-like structure of γ and γ' phases.It is concluded that a solidification rate as high as possible should be used in order to obtain the solidified structure with fine dendrite arm spacing,low microporosity and uniform chemical homogeneity.

STUDY OF INFLUENCE OF POST WELD HEAT TREATMENT ON MECHANICAL PROPERTIES OF RESISTANCE SPOT WELDS FOR 38Cr2Mo2VA STEEL

Tang Jinrong

1991, 11(1): 19-25.

[Abstract](1348) [PDF 957KB](148)

Abstract:
38Cr2Mo2VA steel is a ultrahigh strength steel used in intermediate temperature range.In this paper the mechanical properties of resistance spot welds in three heat treatment conditions were studied.They are single weld pulse,re-heating pulse in the resistance spot welding machine and post weld heat treatment in furnace.Analysis of the microstructure and the stress distribution under loading of weldment shows that the mechanical properties of the spot welds are closely relates to the post weld heat treatment conditions,and can be improved by suitable post heat treatment processes.

THE INFLUENCE OF MICROSTRUCTURE ON IMPACT FATIGUE CRACK INITIATION LIFE OF 40CrNi2Si2MoVA STEEL

Zhu Zixin, Hu Guangli

1991, 11(1): 26-31.

[Abstract](1427) [PDF 940KB](136)

Abstract:
In the present paper,the influence of microstructure on impact fatigue crack initiation life(FCIL)of 40CrNi2Si2MoVA ultrahigh strength steel was investigated.Two kinds of microstructure were adopted by oil quenching and isothermally quenching at 270℃.And overload effect on FCIL was studied.The results show that,the relative sliding of martensite or bainite laths leads to the micro-crack initiating and growing up to a macro-crack.With decreasing retained austenite amount and increasing yield stress,the FCIL will be enhanced.In a certain condition,overload can markedly prolong FCIL.

THE INFLUENCES OF SHORT-AND LONG-EXPOSED TIME AT ELEVATED TEMPERATURES ON THE PROPERTIES AND MICROSTRUCTURES OF ALUMINIUM ALLOY 2024

Wang Shuncai, Li Chunzhi, Shi Jian, Li Chunyu

1991, 11(1): 32-38.

[Abstract](1278) [PDF 1247KB](213)

Abstract:
The influences of short-and long-exposed time at elevated temperatures on tensile properties and microstructures in 2024 T3511 condition have been studied by TEM.The experimental results show that after heat-treatments,the strength curves have passed through a smooth stage and dropped rapidly:the relationship of plasticity and temperature is not a monotonous ruction,there is a lowest plastic value in the middle of curve.The microstructure analysis indicates that there are two types of aging phases:S sequence(forming in G.P.area)and X phase(forming in high temperature),the S aging sequences are as follows:G.P.area→S"→S"+S'→S'+S→S and the X phase forms during precipation of S"+S.The microstructures corresponding to smooth stage of the strength curve are G.P.area and S" phases,and the microstructures,corresponding to the begining drop stage of strength curve and the lowest area of plasticity are S'+S"+X,which is related to semi-coherent S' and X.The drop stage of strengh and the increase stage of plasticity are in relationship with non-coherent S+X Phases in ageing structure.

TENSILE PROPERTIES AND DEFORMATION BEHAVIOR OF SiCw/Al COMPOSITE

Ma Zongyi, Yao Zhongkai

1991, 11(1): 39-43,54.

[Abstract](1357) [PDF 689KB](139)

Abstract:
In this paper the tensile tests of SiCw/6061Al composite were carried out,and the fracture surfaces were analysed by SEM technique.It was found that the proportional limit of the composite and the matrix alloy was approximately same,but the composite exhibited higher work-hardening rate and much higher tensile strength compared to the matrix alloy.The low proportional limit may be explained by localized plastic deformation under low macroscopic stress caused by stress concentrations at the ends of SiC whiskers.High work-hardening rate is related ton pronaunced increase in the dislocation density in the matrix during deformation and whiskers prohibition of microcrack propagation.The fracture surface of the composite consisted of fine dimples indicates the localization of plastic deformation.

THE DEVELOPMENT OF NEW HIGHTEMPERATURE RISISTANT INSULATION VARNISH COMPOUNDED WITH DIPHENYL OXIDE AND ITS APPLICATION

Pan Shunqing, Zhou Shufang

1991, 11(1): 44-54.

[Abstract](1338) [PDF 611KB](207)

Abstract:
The service life of electrical machines is mainly dependent on the lifetime of insulation system,property of which depends to a large extent on the performance of insulation varnish for aircraft electical machines with high rotating speed.The new insulation varnish,compounded with diphenyl oxide and developed by our company,has many advantages:high heat resistance,powerful adhesive strength,large resistance to overloading,good technological chain and lower prices.As a result of replacing traditional silican and polyimide varnishes and removing existing disadvantages of those two kinds of varnishes,the new insulation varnish is sucessfully used in more than 10 kinds of aircraft electrical machines and has obtained a good application benefit.This paper describes in detail the development of sythetic varnish,the research of application property,the result of technological test,the case of using in electrical machines and so on.It can be used as reference for many scientific research and technicians in aerospace departments.

THE FATIGUE PROPERTIES AND LIFE PREDICTION OF CERAMIC MATERIALS

Wang Jian, Jin Zhihao, Wang Xiaotian

1991, 11(1): 55-66.

[Abstract](1406) [PDF 806KB](125)

Abstract:
In this paper fatigue property of ceramic materials is discussed upon lineal elastic fracture mechanism,and the theory and method of life predicton for ceramic materials are introduced.

A REVIEW OF EXPERIMENTAL STUDY ON CORROSION FATIGUE FOR AIRCRAFT STRUCTURAL MATERIALS AND COMPONENTS

Zhang Shijie, Go Hongquan, Niu Kangming, Ouyang Hui

1991, 11(1): 67-77.

[Abstract](1316) [PDF 1155KB](348)

Abstract:
In this paper a review on experimental invistigations on corrosion fatigue of aeronautical structure materils and components was presented.Dominant experimental factors affecting corrosion fatigue behaviour were discussed.

1991 Vol. 11, No. 1