航空材料学报

CREEP FATIGUE INTERACTION BEHAVIOR OF A NICKEL BASED SUPERALLOY AND LIFETIME PREDICTION

Chen Lijia, Wang Zhongguang, Tian Jifeng, Yao Ge

1998, 18(3): 1-7,15.

[Abstract](1352) [PDF 297KB](305)

Abstract:
Creep-fatigue interaction behavior of nickel-based superalloy GH4049 is studied by performing fully reversed total strain controlled low cycle fatigue tests with equal hold in tension and compression,hold in tension or in compression.At higher strain amplitudes, the alloy exhibits cyclic strain hardening followed by softening while a stable cyclic stress response is shown at low strain amplitudes.A significant reduction in fatigue life is observed with hold time in compression or in both tension and compression.The influence of tensile hold on fatigue life is mainly related to the imposed total strain amplitudes.The opposite mean stress develops during tensile and compressive hold tests.Crack initiation and stage Ⅰ growth is transgranular,but crack growth in stage Ⅱ is primarily intergranular.In addition,a linear damage summation method is chosen to predict creep-fatigue lifetime.

SOLUBILITY PREDICTION OF MULTIPLE COMPONENT SUPERALLOYS

Chen Zhiqiang, Han Yafang, Zhong Zhengang, Wei Pengyi, Yan Minggao

1998, 18(3): 8-15.

[Abstract](1321) [PDF 760KB](465)

Abstract:
Considering the effect of atomic radius,electronegativity and out-shell electronic number of solute and solvent elements on the solubility of solute, solubility (C) equation of binary alloys was derived: C = A1(ΔR)+A2(ΔN)2+A3(ΔE1/3)+A4.Constant A1,A2,A3 and A4 was acquired from binary nickel base alloys.A new prediction method of solubility based on this equation was proposed for calculating γ/(γ+σ) and γ/(γ+μ) boundary curves of nickel cobalt base ternary alloys phase diagrams.The calculated boundary curves are in well correspondent with experimental curves.Compared with boundary curves predicted by Md method,its accuracy was higher than that of Md method.

INTERNAL STRESS AND EFFECT FACTORS FOR SINGLE CRYSTAL NICKEL BASED SUPERALLOYS DURING STEADY STATE CREEP

Tian Sugui, Zhang Jinghua, Jin Tao, Yang Hongcai, Xu Yongbo, Hu Zhuangqi

1998, 18(3): 16-21.

[Abstract](1375) [PDF 576KB](197)

Abstract:
The creep resistance of two single crystal nickel based superalloys with orientation has been studied by the internal stress measurement of dislocation motion,EDAX composition analysis and TEM observation.It is shown that the size and volume fraction of γ′ phase in Alloy 2 are obviously decreased with the temperature rise.The main reason for a better creep resistance of Alloy 1 during steady creep is that this alloy contains a higher volume fraction of γ′ phase due to higher Al,Ta contents.

STUDY ON SUPERPLASTIC OPTIMAL DEFORMATION PATTERN IN Ti-15-3 TITANIUM ALLOY

Wang Gaochao, Liu Zhenhua, Du Zhongquan

1998, 18(3): 22-28.

[Abstract](1443) [PDF 257KB](265)

Abstract:
The superplasticity of Ti-15-3 titanium alloy is studied at two deformation patterns,i.e.,constant velocity and strain rate cycling,respectively.Also discussed are the principles and experimental methoes of computer optimization.The test results show that ,through deformation of strain rate cycling,the titanium alloy can also produce rather better superplastie behavior although it has not undergone grain refinement treatments.The computer optimization can help to develop better superplasticity and optimize superplastic deformation patterns.

MICROSTRUCTURES AND MECHANICAL PROPERTIES OF CAST TiAl ALLOYS

Zhang Ji, Zhang Zhihong, Zou Dunxu, Zhong Zengyong

1998, 18(3): 29-33.

[Abstract](1449) [PDF 203KB](391)

Abstract:
The effects of alloying elements,Cr,V,Nb,on the cast microstructure have been analyzed on the basis of the metallographical observations of the cast microstructures in several TiAl alloys.It is found that the TiAl alloys alloyed with V and/or Cr tend to form the columnar crystal macrostructure and exhibit preferredly arranged lamellar microstructures under certain casting conditins.The TiAl alloys containing Nb can have equiaxed macrostructures and homogeneous fully lamellar microstructures on the same casting conditions.The mechanical properties of the cast alloys have been evaluated by the 4 point bending test as well.

NUMERICAL ANALYSIS ON EFFECT OF PLATE WIDTH ON STRESS DISTRIBUTION IN WELDBONDED JOINTS

Chang Baohua, Shi Yaowu, Dong Shijie

1998, 18(3): 34-39.

[Abstract](1320) [PDF 231KB](254)

Abstract:
Using three dimensional elastoplastic finite element method(FEM),the effect of plate width on stress distribution in weldbonded joints has been analysised numerically.Two kinds joints are made with different types of adhesives,one of which is phenolic resin of higher elastic modulus and the other is acrylic resin of lower elastic modulus.Results show that:for the phenolic resin joints,there exist greater stresses at the edge of the lap region than that at the edge of the spot weld.Cracks are initiated at the ege of the lap region.When the plate width increases,peak stresses at the edge of the lap region and the spot weld both decrease.The joint strength will be improved if the fracture mode of the joints does not vary.For the acrylic resin joints,much greater stresses are found at the spot weld edge than that at the lap region edge,so that fracture begins from the edge of the spot weld in stead of at the edge of the lap region.With increase of the plate width,stress variation around the spot weld is practically negligible.Thus increasing the plate width has no apparent effect on the joint strength and the joint fracture mode.

EFFECT OF ALLOY POWDER ON MICROSTRUCTURE OF BRAZING SEAM

Zhang Junying, Tian Wei, Sun Jisheng, Liu Xiaofang

1998, 18(3): 40-45.

[Abstract](1229) [PDF 232KB](149)

Abstract:
Change of K3 superalloy joint microstructure especially boride phases was investigated in this paper. The function and adding method of alloy powder were also discussed. Results have shown a decrease in the concentration of B and Si elements and eutectic phases in the brazing seam with the adding of alloy powders, so to improve the joint microstructure. This method has been proved to be an effective way to increase the mechanical properties of the brazing joints.

ADHESION AND FRAGMENTING OF DIAMOND FILMS DEPOSITION ON HARD METAL

Li Chengming, Wang Jianming, Xu Zhong, LüFanxiu

1998, 18(3): 46-50.

[Abstract](1424) [PDF 223KB](153)

Abstract:
Adhesion of diamond films deposited on WC-6%(YG6) with different pretreatment has been studied. It was found that adhesion of diamond films and hard metal substrate was greatly increased. “Anchoring effect” produced by excimer laser irradiation is considered as the main reason for high adhesion strength by excimer laser pretreatment.

CALCULATION OF FRACTURE TOUGHNESS BASED ON DAMAGE THEORY FOR RESIN MATERIALS

Liu Yuanyong, Ge Dongyun

1998, 18(3): 51-56,61.

[Abstract](1455) [PDF 257KB](195)

Abstract:
The analogy of damage growth between the deformation in property test and the crack growth is discussed.A model calculated the fracture toughness of material using the material property is developed based on the damage theory including the effect of microcracks and flaws at the tip of crack.The numerical results are presented and compared with available experimental data for typical toughened epoxy resins.The method is possible to use for other polymers.

STUDY OF LAMINATED GLASS MECHANICAL MODEL

Ma Juanrong, Zang Shuguang, Ding Limei

1998, 18(3): 57-61.

[Abstract](1416) [PDF 232KB](365)

Abstract:
According to experimental stress analysis results of laminated glass and plate elastic theory,the paper presents two kinds of mechanical models and calculating methods.One is to deal with isotropic continuous laminated glass using compound rigidity matrix.Amother is to calculate the single piece glass through resolving the exterior force.In accordance with the different stress state of laminated materials with different elastic modulus,a precise and practical stress distribution can be obtained by adopting finite element numerical calculation.

1998 Vol. 18, No. 3