航空材料学报

Effects of Y on Compression Properties of Ti-23Al-25Nb Alloy

SI Yu-feng, CHEN Yu-yong, KONG Fan-tao, LIU Zhi-guang

2006, 26(6): 1-5.

[Abstract](1656) [PDF 639KB](215)

Abstract:
Microstructures and phase compositions of Ti-23Al-25Nb alloy after different heat treatment were analyzed by SEM and XRD.The form of element of Y in original structure was analyzed by TEM.The results show that the element of Y is in the form of Y2O3.Being as the addition of element of Y,diffraction peaks of O-phase increase,and the compression properties of Ti-23Al-25Nb alloy such as compression strength and compressibility increase.Strengthening effect of Y is the result of combined action of dispersion strengthening of Y2O3 and grain boundary strengthening of Y.

Multiaxial Fatigue Behavior of GH4169 Superalloy under Non-Proportional Loadings at High Temperature

SHANG De-guang, SUN Guo-qin, CAI Neng, WANG Jian-guo, WANG Lian-qing, WANG Hong-ying

2006, 26(6): 6-11.

[Abstract](1753) [PDF 272KB](412)

Abstract:
Multiaxial fatigue behavior of superalloy GH4169 was investigated by using the thin tubular multiaxial fatigue specimens under proportional and non-proportional loadings at high temperature.The relationship between the cyclic stress response and the cyclic number was studied by recording the experimental data.The experimental results showed that the fatigue life was decreased under nonproportional loading.In the entire fatigue process,the torsional stress response always showed the cyclic softening.The characteristics of cyclic hardening or softening for tensional stress response depended on the strain loading paths and the loading parameters.With the cyclic number increase,the creep phenomenon was gradually showed under multiaxial loading at high temperature.

Fatigue Crack Growth Experiments and Model in Corrosive Environment for Aluminum Alloy

BAO Rui, DONG Yan-min, ZHANG Jian-yu, FEI Bin-jun

2006, 26(6): 12-16.

[Abstract](1707) [PDF 852KB](345)

Abstract:
Experiments with CCT specimens of 2024-T3 aluminum alloy in 4 kinds of typical environments were conducted and a corrosion fatigue crack growth model was presented.The discussion based on the testing results shows that the model has a great capability in describing the corrosion fatigue crack growth rate as well as predicting crack growth life in different environments and the influence of corrosion can be understood clearly by the corrosion modification factors.Via averaging these factors in mono-medium environments in weight,the model can also be applied to the analysis of crack growth in perplexing environments reasonably.The model has a great advantage for the full usage of the existing crack growth probability data of materials.

Improving of Frequence Method and Its Application in Damage Identification

DONG Xiao-ma, ZHANG Wei-gong

2006, 26(6): 17-20.

[Abstract](1363) [PDF 184KB](268)

Abstract:
The traditional damage location index based on frequence was obtained by ignoring the second rank term in structural movement disturbed equation.There was likely to exist miscarriage of justice when it was applied to identify structural damage location.On the base of the traditional method,an improved method of frequence was given.Finally,the results of numerical value simulation experiment of composite material cantilever girder showed that the improved method was more effective than original method.

Friction Stir Welding Process of 01420 Aluminum-Lithium Alloy

WEI Shi-tong, HAO Chuan-yong

2006, 26(6): 21-25.

[Abstract](1700) [PDF 605KB](359)

Abstract:
The friction stir welding of 2mm thick 01420 Al-Li alloy was conducted,the microstructures,qualities of joining,and mechanical properties of the joints as well as the influences of welding parameters on the alloy were investigated,meanwhile comparing the mechanical properties with that of the joint welded by argon arc welding.The results show that if the welding parameters are optimal,good appearance welds are achieved,the tensile property of weld can attain 77% that of the base metal,and the bending angle can reach 180°,which is higher than those of the joint welded by argon arc welding.

Effect of Solid Particles Erosion on Erosion Resistance of ZrN Coated Titanium Alloy

WU Xiao-mei, LI Wei-guang, LU Feng

2006, 26(6): 26-29.

[Abstract](1669) [PDF 577KB](356)

Abstract:
ZrN coating was deposited on TC11 substrate by multi-arc plating,erosion resistance of ZrN coating was evaluated by solid-particle erosion testing using differential particles at differential impact angle and impact velocity,the surface and cross-sectional microscopy were examined in a scanning electron microscopy(SEM).It was found that the erosion rate of ZrN coating was increasing with particles hardness,impact angle and impact velocity under the same impact condition,ZrN coating had the maximum erosion at 90° impact angle,ZrN coating demonstrated markedly improvement in erosion resistance performance of TC11 titanium alloy.

Residual Stress Field Induced by Laser Peening:a Finite Element Analysis

PENG Wei-wei, LING Xiang

2006, 26(6): 30-37.

[Abstract](1800) [PDF 1281KB](471)

Abstract:
A non-linear elastic-plastic finite element method to predict the residual stress distribution induced by Laser Shock Processing(LSP) in the AISI 304 stainless steel was established.This two dimensional FEA model considered the dynamic material properties at high strain rates(106s-1) and the precise determination of loading conditions. Effects of laser power density,laser spot size,laser pulse duration,multiple LSP processes and one/two-sided LSP on the compressive stress field in the stainless steel were(evaluated) for the purpose of optimizing the process.Numerical results have a good agreement with the measurement values by X-ray diffraction method and also show that the magnitude of compressive stress induced by laser shock processing is more than the welding residual stress.Therefore,laser shock processing is an effective method for protecting weldments against stress corrosion crack.

Coarsening of γ′ Precipitates in a Nickel-Based Superalloy Prepared by EBPVD

HAN Jie-cai, LI Xiao-hai, CHEN Gui-qing, MENG Song-he

2006, 26(6): 38-41.

[Abstract](1844) [PDF 1464KB](295)

Abstract:
The sheet metal of a new Nibased superalloy was prepared by Electron Beam Physical Vapor Deposition(EBPVD) technology.Microhardness tester and transmission electron microscope were used to study the change of room temperature microhardness,coarsening behavior and morphological change of γ′ precipitates.Results show that γ′ precipitates coarsened by the step growth mechanism change from approximately round shape to regular order cubic one with the increase of aging temperature.Growth of γ′ precipitates proceeds by Ostwald ripening controlled by volume diffusion of solute atoms.The activation energy for growth are evaluated as 266.18kJ·mol-1 for this alloy.The decrease in room temperature microhardness and the softening of alloy can be attributed to the growth of γ′ precipitates in the alloy.

Influence of Y-Addition on the Long-Term Oxidation Behavior of High Nb Containing TiAl Alloys

ZHANG Ning, LIN Jun-pin, WANG Yan-li, CHEN Guo-liang

2006, 26(6): 42-45.

[Abstract](1795) [PDF 1192KB](429)

Abstract:
Influence of Y-addition on the long-term oxidation behavior of high Nb containing TiAl alloys was studied.The results showed that the oxidation rates,structures of scale as well as the scale spallation resistance were closely related to the concentrations of Y.Under isothermal oxidation at 900℃,a small amount of Y-addition(0.4at%) was effective in improving the oxidation resistance.However,the alloys with higher Y contents(0.6 and 0.8 at%) had a detrimental effect on the oxidation resistance after initial isothermal exposure.Oxidized samples were examined by scanning electron microscopy(SEM),energy dispersive x-ray analysis(EDX) and x-ray diffraction analysis(XRD),it was found that a small amount of Y-addition(0.4at%) was effective in improving the oxidation resistance by refineing the oxide particles,promoting formation of a protective continuous Al2O3 scale and improving the adherence of the oxide scale.

Study on Spark Change Regularity during Plasma Anodizing on Magnesium Alloys

ZHANG Rong-fa, HE Xiang-ming, SHAN Da-yong, HAN En-hou

2006, 26(6): 46-49.

[Abstract](1794) [PDF 639KB](308)

Abstract:
In Magoxid process,the plasma anodizing process on magnesium was studied.It was classified into three stages: traditional anodization,micro-arc anodization and arcing.With anodization proceeding,the applied voltage increased and the transition from micro-arc to arcing stage took place.Initially,both micro-arc and arcing sparks mainly concentrated on edges of the sample and then covered the entire surface.Compared to micro-arc stage,the sparks on arcing decreased greatly in number,became bigger and their lifetime increased.Corresponding to spark changes,the pores of anodic coatings decreased in number but increased in diameter.After 10 min anodization,anodic coatings turned to no evidently porous structure.

Test Research of Damping Performance of Metal Rubber Damper at High-Low Temperature

HOU Jun-fang, BAI Hong-bai, LI Dong-wei, WANG You-yan, TAO Shuai

2006, 26(6): 50-54.

[Abstract](1720) [PDF 775KB](382)

Abstract:
Considering the strong nonlinear characteristics of Metal Rubber(MR) material in the axial direction,the original method of damping measurement based on curve fitting was improved in order to eliminate the error of fitting,and the accuracy was advanced.To meet the need of reducing vibration in extreme conditions such as at high or low temperature,the fixed disc MR damper was designed and the test research on its damping performance at high-low temperature was made.Results showed that MR damper designed exhibited good and stable damping performance with the temperature ranging from-70 to 300℃,and its dynamic average rigidity descended with the rising temperature.The dependence of its damping performance and bearing capacity on temperature was far smaller than that of viscoelastic material.

An Investigation on Interface and Tensile Strength of SiC/Ti-153 Composites

CAI Shan, LI Zhan-yi, DONG Yan, YAN Ming-gao

2006, 26(6): 55-59.

[Abstract](1579) [PDF 815KB](298)

Abstract:
The interfacial reaction in SiC/(B4C+C)/Ti-153 composite were studied by thermodynamic calculation and reaction products were analysised by EDX and XRD.The results showed that reaction products were TiC,TiB and TiB2.Tensile strength of composites after different hot pressing process and with different fracture surface was also investigated by tensile test and SEM.The results indicated that tensile strength was affected by the state of interface.Finally,the tensile strength of composite with different thickness of interfacial reaction layer after different heat-treatment process was evaluated,it was found that with increasing of thickness of interfacial reaction layer,the tensile strength of composites declined.

Study on Microstructue and Mechanical Properties of Nano CaCO₃/PPS Composite

LONG Sheng-ru, HUANG Rui, YANG Jie, LIU Xiao-bo

2006, 26(6): 60-63.

[Abstract](1667) [PDF 586KB](391)

Abstract:
Composites of polyphenylene sulfide reinforced with calcium carbonate nanopowder were prepared by compression molding.The distribution and morphology of fillers were characterized by transmission electron microscopy(TEM).By using atomic force microscopy(AFM),the detailed microstructure and fracture surface of the composite could be observed.The result showed that the average particle size of the CaCO3 nanoparticles was about 56nm,tensile tests showed that the tensile strength was 83.73MPa when the addition was 10wt%,impact stress was 74.13kJ/m2 when the addition was 5wt%.

Shear and Compress Experimental Study on 3-D Braided C/SiC Composites

WANG Bo, JIAO Gui-qiong, CHANG Yan-jun, PAN Wen-ge

2006, 26(6): 64-67.

[Abstract](1678) [PDF 271KB](407)

Abstract:
Shear and compress tests of 3-D braided C/SiC composites were carried out,and load-displacement curves and shear strength,compress strength were gained.The following conclusions were reached.With the same width,average shear strength of specimens of greater height was less than that of specimens of lower height.With the same shear cross section area,average shear strength of XY shear specimens was greater that of YX shear specimens.And with the same cross section,compress strengths in X direction of specimens with different height were almost the same.FEA results revealed that maximum shear stress and compress stress of 3D braided C/SiC structure were less than material's strength.

Compressive Behavior of 3-D Kevlar/Epoxy Woven Composites at Various Strain Rates

GUO Xu, LI Wang, QIU Yi-ping

2006, 26(6): 68-71.

[Abstract](1612) [PDF 237KB](296)

Abstract:
The compressive properties of 3-D Kevlar/epoxy woven composites at quasi-static and high strain rate loadings were investigated to evaluate the compressive failure mode at different strain rate.The through-thickness compressive properties at high strain rates were tested using the split Hopkinson bar(SHPB) technique.The compressive properties at quasi-static strain rate were also tested and compared with those at high strain rates.The results indicate that the stress-strain curves are rate sensitive and compressive stiffness,maximum compressive stress of the 3-D Kevlar/epoxy woven composites linearly increase with the strain rate.The compressive failure of the composites specimen tends to be in shear failure mode and it is completely broken at high strain rates while only compressive deformation can be observed in quasi-static loading.

Hydrothermal Effects on Cured Cyanate Ester Resin Modified by Poly Vinyl Pyrrolidone

WANG Jie-liang, LIANG Guo-zheng, ZHAO Wen, LüSheng-hua, MA Xiao-yan

2006, 26(6): 72-76.

[Abstract](1743) [PDF 920KB](280)

Abstract:
Poly vinyl pyrrolidone(PVP) was employed to improve the toughness of bisphenol A dicyanate ester resin.Hydrothermal performance of the modified systems was systematically studied.Moisture takeup of the cured resins increased with the increasing of the weight percentage of PVP.Mechanical properties of the modified systems were largely improved by the introducing of PVP.The residual flexural and impact strength after ageing were improved from 38.8% and 35.5% to 86.8% and 66.1% respectively when 5wt% of PVP were introduced.On the same time,however,the introducing of PVP had little influence on the thermal performance,dielectric properties and shape stability.The modified system with 5wt% PVP showed the best performance overall.

Brittle-to-Ductile Transition of Poly(Butylene Terephthalate) Synergistically Toughened by POE-g-MAH and PC

WEI Gang, PENG Ya, LONG Sheng-ru, HUANG Rui

2006, 26(6): 77-80.

[Abstract](1723) [PDF 702KB](489)

Abstract:
The brittle-to-ductile transition of poly(butylene terephthalate) synergistically toughened by anhydride grafted poly(ethylene-octene) copolymer elastomer(POE-g-MAH) and thermoplastic resin(PC) was investigated.The morphologies of dispersion phase and fractured surfaces were observed and analyzed with the help of scanning electron microscope(SEM).And the toughening mechanism was also approached.The brittle-to-ductile transition of the blends was observed at a lower POE-g-MAH content for the addition of PC.When POE-g-MAH content was up to 10%,the notched impact strength of the blend with PBT/PC mass ratio of 50/50 was up to 78kJ/m2,with the tensile strength up to 52.5MPa.SEM micrographs showed that the dispersed phase of PC took a very irregular microstructure of slat-like or plate-like shape at higher content of PC.It should be noted that the particular phase morphology of PC covered with a soft layer of POE-g-MAH was the principal mechanisms of strengthening and toughening of the ternary blends.

2006 Vol. 26, No. 6