航空材料学报

INFLUENCE OF GRAIN SIZE ON THE LOW-CYCLE FATIGUE FOR TURBINE DISC OF GH33 SUPERALLOY

Zhou Ruifa

1981, 1(1): 1-9.

[Abstract](1394) [PDF 1584KB](151)

Abstract:
In this paper,the test specimens choose fine and coarse grain from the turbine disc of GH33 superalloy.The Low-Cycle is measured at 650℃.Experiment results show that coarse grain seriously reduces the Low-Cycle fatigue properties.It has been proved by means of fracture analysis.In addition to this,it was found that the relation between stable stress(σST) and fatigue life (Nf) is linear on log-log coodinate axis both fine and coarse grain,as follows: Nf=(σ′f/σST)-b Finally,the effect of grain size and mechanism of fatigue fracture was discussed yet.

EFFECT OF TRANSFORMED BETA MORPHOLOGY AND OTHER STRUCTURAL FEATURES ON MECHANICAL PROPERTIES IN Ti-6Al-4V

Cao chunxiao, Wang Jinyou, Shen guiqin

1981, 1(1): 10-15.

[Abstract](1394) [PDF 1418KB](146)

Abstract:
A study of the relations between structures and properties in Ti-6Al-4V alloy shows that tensile ductility,fatigue strength(HCF and LCF),fraeture toughness. creep resistance and other properties not only depend on whether it's an acicular or an equiaxed structure,but also depend on primary alpha percentage, prior beta grain size,transformed beta morphology and other conditions. Among these conditions,the transformed beta morphology is an especially important factor.For a certain property,an acicular structure is better than a structure containing equiaxed alpha in one condition,but the former may be similar to or poorer than the latter in another condition.Therefore, it's not correct to compare these two types of structures unconditionally.Among all structures mentioned in this paper,comparison Of the combination of various properties shows that the basket-weave structure is the best and the aligned structure is the poorest.

THE DEFORMATION LAW IN SINGLE-AXIAL TENSION FOR ALUMINIUM ALLOY LC9

Huang Daqian, Yu Wenfang

1981, 1(1): 16-21.

[Abstract](1526) [PDF 464KB](135)

Abstract:
In the present work,the work-hardening of an Aluminum alloy LC9 bar deformed by tension at room-temperature was investigated.The true stress-stain curve was measured.The stress-stain relation for homogeneous stage and inhomogeneous stage of deformation were obtained.The stress revision in respect of necking zone was made.The surface of the neck of the sample was briefly discussed.

THE INVESTIGATION ON HEAT-RESISTANT PROPERTIES OF Mg-Y-Zn-Zr SYSTEM MAGNESIUM CASTING ALLOYS

Zhao Zhiyuan, Ge Laichun, Qiao Dougfu

1981, 1(1): 22-29.

[Abstract](1414) [PDF 1208KB](137)

Abstract:
In this paper the relationship between the compositions,mechanical pro-perties or microstructures of Mg-Y-Zn-Zr system casting alloys has been studied.It has been found that the ratio of Yttrium and zinc content in composition of this alloy will affect its properties and structures.When the Y/Zn ratio equals to about 1.5,the phases at the grain boundaries present a lot of white massive compounds in the form of Mg30YZn and a little of(αMg+Mg48Y5Zn5) eutectics.This kind of structure contributes the best creep property at high temperature.

INVESTIGATION ON MICROSTRUCTURE IN SHOTPEENING SURFACE STRAINING LAYER OF MATERIALS

Wang Renzhi, Li Xiangbin, Yin Yuanfa, Yan Minggao

1981, 1(1): 30-38.

[Abstract](1380) [PDF 1720KB](255)

Abstract:
The microstructure in shot-peening surface plastic straining layer of several softening and hardening materials are investigated.it was found that this plastic strain is not the same of simple monotonic plastic strain,but a cyclic plastic strain.As a result of cyclic strain,material in the surface layer subjects to"cyclic hardening/softening"as it changes in the strain fatigue test. The appearence of cyclic hardening/softening depends on the virgin microstructure of materials and the shot-peening intensity.For the softening materials, the cyclic hardening is taken place during shot-peening,while for the hardening materials (martensite or maraging steels),the cyclic softening is taken place at first,then cyclic rehardening is followed during shot-peening.It was found that the cyclic hardening/softening behaviours in the shot-peening surface layer are dependent on the variations of subgrain size,lattice distortion and excess dislocation density in the materials.

THE DISTRIBUTION AND EFFECT OF SILICON IN Al-Si COATINGS-ON INVESTIGATION OF Si-CONTAINING BARRIER

Cai Yulin, Zheng Yunrong, Mo Longsheng, Yang Zhonglin

1981, 1(1): 39-44.

[Abstract](1387) [PDF 4114KB](193)

Abstract:
The distribution and existential form of silicon in Al-Si coatings were investigated in this paper.The Si-rich M6C barrier formed in Si-containing aluminide coatings is revealed.The barrier impedes Al and Si diffusion into matrix of alloy,therefore rises oxidation resistance of this coating at high temperature.By means of process control or pretreatment the Si-rich M6C barrier may be formed.

ON PREDICTION OF THRESHOLD ΔK VALUE FOR FATIGUE CRACK PROPAGATION

Yan Minggao, Yu Chunghua

1981, 1(1): 45-49.

[Abstract](1325) [PDF 278KB](105)

Abstract:
Based on an analysis of the criticalcondition for plastic-blunting at a crack tip and the effect of stress ratio R on FCP in metals,a general expression for calculating the threshold intensity factor range ΔKth may be suggested: ΔKth=Eεf√2πρmin1/2(1-R)γ Where ρmin is the relevant Burgers vector,|B|.It is found that the calculated values are fairly consistent with the existing experimental results.

AN INVESTIGATION OF HIGH TEMPERATURE LOWCYCLE FATIGUE CRACK GROWTH RATES FOR DIRECTIONALLY SOLIDIFIED ALLOY K5

Liu Shaolun, Xie Jizhou

1981, 1(1): 50-58.

[Abstract](1380) [PDF 1048KB](173)

Abstract:
The high temperature low-cycle fatigue crack growth rates of a Ni-base alloy K5 in direetionally solidified and conventionally casted forms have been deter-mined by eteetro-potential method.The experimental resttlts have been analysed by linear elestic fracture mechanics parameter ΔK and elestic-plastic fracture mechanics parameter ΔJ,respectively.It is shown that 1.The high temperature low-cycle fatigue crack growth rates of alloy K5 may be characterized by stress intensity range ΔK. 2.At 700℃,the da/dN of directionally solidified alloy K5 is slightly lower than that of the conventional cast,however,at 950℃,the former is oboviously lower than the latter.The difference is about 2.3 to 3.7 times when ΔK increased from 80 to 150 kg.mm-3/2. 3.Under 700 and 950℃,the crack formation periods Ni at 1 mm crack length of directionally solidified are considerably longer than that of the conventional one,the difference is about 1,4 and 4 times,respectivelly.

THE ANALYSIS OF ROTATIONS IN CRYSTALS

Li Chuuzi

1981, 1(1): 59-66.

[Abstract](1407) [PDF 416KB](231)

Abstract:
For the rotation of the triclinic axes about some axis through any angle the linear transformation between new set of axes and old one has been treated, and the transformation matrix is presented.The transformation matrix of the components of some vector rotated about an arbitrary axis by any angle in any crystal structure has been derived,and a convenient approach for calcu-lating these components is presented.An important application of this matrix method is to treat twinning rotations other than 180°.

ALGOL COMPUTER PROGRAM OF DATA REDUCTION TECHNIQUES FOR CONSTANTLOAD-AMPLITUDE FATIGUE CRACK GROWTH RATES

Zhang Yongkui, Gu Mingda

1981, 1(1): 67-79.

[Abstract](1589) [PDF 766KB](232)

Abstract:
In this paper,ALGOL computer program of data reduction techniques for fatigue crack growth test is described. There are the following characteristics in this program,such as:using the seven points incremental polynomial method for processing crack length a versus number of cycles N data and some modifications of the FORTRAN computer program recommended byASTM E647-78T;processing data of either compact type(CT)or center-cracked-tension(CCT) specimens by Paris formula or Forman formula;according to the criterion of linear elastic fracture mechanics,checking the data against the size requirements;employing the probability statistical method for identifing the variability or scatter in da/dN data,in terms of a variability factor VF,defined as VF=exp(4S), where S is the residual standard deviation and finally giving the probability scatter band of confidence level 950%,etc. Using this program,the following information can be tabulated for each test by computer:a,N;ΔK,da/dN;material constants C,n(or m);the [(1-R) Kc-ΔK] da/dN vs ΔK curve and the life prediction value for a crack specimen,etc. A great amount of practices showed that the present ALGOL computer program is a rather simple and convenient method which can be used satisfa-ctorily in analysing the results fatigue crack growth tests.

SOLUTIONS OF CLOSE FORM FOR ESTIMATING CRACK PROPAGATION LIVES OF STRUCTURAL MEMBERS

Zhang Xing, Wu Hehua

1981, 1(1): 80-86.

[Abstract](1416) [PDF 369KB](219)

Abstract:
In this paper,according to some retardation models,we have derived the following analytic solutions hkclxb-19810111-86-1.png (for Matsuoka's model) (for He's model and Huang's model) to estimate the crack growth lives of structural members under the condition of loadings of short periods,which are encountered frequently in aircraft.It can be proved that the corresponding two linear accumulative damage formulae are (for preceding first solution) (for preceding second solution) whcrce,α、β and γ are coefficient and exponents respectively in the Walker's formula,n=β+γ,φ_i is a factor of modification determined by the applied retardation model. The fall-scale fatigue testings of landing gear show that the crack propa-gation life predicted with our first formula gives satisfactory and somewhat couservative result.

STUDY OF THE RELATIONSHIP BETWEEN THE MECHANICAL PROPERTIES AND TEXTURES IN TITANIUM ALLOYS

Ni Hengfei, Zhang Guohuan

1981, 1(1): 87-96.

[Abstract](1509) [PDF 637KB](257)

Abstract:
In this paper,a brief review on the relationship between the mechanical properties and textures in titanium alloys was made.The types of textures and the influence of various factors on the textures in commercial titanium alloys were described.The effects of textures on the elastic modulus,yield and tensile strength,fracture and fatigue properties as well as some pro-blems on the application of texture strengthening were discussed.

1981 Vol. 1, No. 1