航空材料学报

Research on High Temperature Deformation Behavior of New Type Nickel-Based P/M Superalloy

WU Kai, LIU Guo-quan, HU Ben-fu, LI Feng, ZHANG Yi-wen, TAO Yu, LIU Jian-tao

2010, 30(4): 1-7.

[Abstract](1616) [PDF 2035KB](296)

Abstract:
The high temperature deformation behavior of a new type 3rd generation nickel-based powder metallurgy(P/M) superalloy FGH98Ⅰwas studied in the different deformation temperatures(950～1150℃) and different strain rates(0.0003～1s-1) using Gleeble-1500 thermal simulator.It developed the dynamic RTT curve and established the constitutive relationship of hot deformation.The results show the flow stress decreases with increasing deformation temperature and decreasing strain rate.The flow stress represents as the characteristic of dynamic crystallization with the increasing of strain at the deformation temperature lower than 1100℃ and strain rates higher than 0.0003s-1.The beginning time of dynamic crystallization has no linear relationship with deformation temperatures in the condition of the strain rates lower than 0.01s-1.Besides,the experiments verify that the sinh model including the variable of strain reflects the changing law of flow stress during the hot deformation process.

Study on Holding Time of β Zone Heating of Titanium Alloy

SHA Ai-xue, LI Xing-wu, CENG Wei-dong, ZHANG Chi

2010, 30(4): 8-11.

[Abstract](1477) [PDF 402KB](260)

Abstract:
Heating process of titanium alloy under different heating pattern was simulated by DEFORM software and the effect of holding time in beta phase on tensile property of TC18 titanium alloy was also studied through heat treatment test.Simulating results show holding time in beta phase is shortened obviously when heating by stage.Preheating temperature also has effect on holding time in beta phase.Holding time in beta phase is cut off 1/3~1/2 while preheating temperature raised from 800℃ to 840℃.Heat treatment test results show that the ductility of TC18 titanium alloy reduces obviously when holding time in beta phase is over 60min.

Microstructures and Properties of Friction-Stir Welded Joint of 2195 Al-Li Alloy

SHU Biao, GUO Xu-ming, ZHANG Chun-xu

2010, 30(4): 12-15.

[Abstract](1649) [PDF 1227KB](226)

Abstract:
In order to determine the effects of friction stir welding on both microstructures and properties of 2195 Al-Li alloy,the friction stir welding experiments with different welding parameters were carried on this alloy.Microstructures and mechanical properties were analyzed.The results indicate that the welded joint is composed of three distinctive zones: welded nugget zone(WNZ),thermo-mechanically affected zone(TMAZ),heat affected zone(HAZ).When welding speed υ=100 mm·min-1,the rotating speed ω is between 700r/min and 1300r/min,the tensile strength of the welded joints decreases with the rotating speed improving;when rotating speed ω=1000r/min,the welding speed υ is between 60mm·min-1 and 140mm·min-1,the tensile strength of the welded joints raises with the welding speed increasing.Joint strength coefficient is 73% at ω=1000rpm,υ=140mm·min-1.The hardness of the welded joint decreases obviously.

Effect of Heat-treatment on Constrained Recovery Stress of Ni₄₇Ti₄₄Nb₉ Shape Memory Alloys

YANG Gen-lin, WANG Xiao-zhen, WANG Er-min, HAN Jin, NI Zhi-ming

2010, 30(4): 16-20.

[Abstract](1652) [PDF 1101KB](227)

Abstract:
The effects of heat-treatment on constrained recovery stress of Ni47Ti44Nb9 shape memory alloys were investigated.The influence of temperature and the strain on recovery stress was studied by the mechanical tester and the PC controlled dilatometer.Transition strain of Ni47Ti44Nb9 alloys increases remarkably with the decreasing temperature.The residual strain decreases and the elastic recovery strain increases slightly with decreasing the deformation temperature.Residual martensite phase appears when heating the constrained Ni47Ti44Nb9 to 150℃.The recovery stress increases rapidly when the temperature reaches the As temperature,and maximizes at 150℃.The recovery stress depends on the temperature:the decrease of temperature lead to the decay of the recovery stress.Thermal cycling treatment has on significant effect on the recovery stress.

Effect of Solid Solution Heat Treatment on Microstructure and Mechanical Properties of 2xxx/SiC_p Aluminum Matrix Composite

HE Xiao-lei, LI Pei-yong, LI Wei

2010, 30(4): 21-25.

[Abstract](1651) [PDF 684KB](255)

Abstract:
A 2xxx/SiCp composite was produced by rapidly solidified powder metallurgy(RS/PM)process.The microstructure and mechanical properties of the composite were investigated by means of SEM,EDS,tensile testing and hardness testing,respectively.The results show that massive solvable phases—θ&S and a minute quantity of insoluble phase AlCuFe existed in the matrix at 485℃.With the increase of solid solution treatment temperature,the solvable phases dissolved in matrix gradually.When the solid solution treatment temperature arrived at 550℃,the solvable phases dissolved thoroughly and only a minute quantity of insoluble remained in the matrix.The composite exhibited higher tensile strength and plasticity when the solid solution treatment temperature was 490~500℃.While the temperature of quenching agent(water)was above 60℃,the strength of composites started to decease.Brinell hardness of the composite increase rapidly and the effect of aging hardening was improved obviously after natural aging for 60 minutes.

High Temperature Oxidation Properties of Al₂O₃ Coating on TiAl Alloy Fabricated by Cathodic Microarc Deposition Method

LI Xi-jin, XUE Wen-bin, CHENG Guo-an

2010, 30(4): 26-30.

[Abstract](1505) [PDF 1061KB](183)

Abstract:
A Al2O3 coating with the thickness of 80μm was prepared on the surface of TiAl alloy in Al(NO3)3 electrolyte by cathodic microarc deposition technology.The isothermal oxidation test was performed under 900℃ in atmosphere environment.Before and after high temperature oxidation,the morphology,microstructure and phase constitutions of the coating were detected by X-ray diffraction(XRD),energy dispersive spectroscopy(EDS) and scanning electron microscopy(SEM).After isothermal oxidation,the coating was intact and adhesive well to the substrate.The mainly constitutions of prepared coating were γ-Al2O3 and a small amount of γ-Al2O3.In addition,amount of Rutile-TiO2 was detected in the coating after oxidation test.The anti-oxidation property of TiAl alloy was improved obviously by as prepared Al2O3 coating at 900℃.

Study on Solid Particle Erosion Behaviors of ZrN Gradient Coatings Prepared by Ion Assisting Arc Deposition

LIU Dao-xin, XI Yun-tao, HAN Dong, ZHANG Xiao-hua

2010, 30(4): 31-37.

[Abstract](1545) [PDF 1357KB](295)

Abstract:
ZrN gradient coatings with different structure and thickness were prepared on nitrided 2Cr13 stainless steel surface by ion assisting arc deposition method for improving solid particle erosion(SPE) resistance of the steel at high impingement angle.The influence of ZrN gradient coating structure and thickness on bonding strength,micro-hardness,ductility,supporting capacity under static and dynamical load conditions and the SPE behaviors of the coatings was investigated.The results show that the duplex surface treatment layer with high supporting capacity,continuous interface stress and strain distribution,good bonding strength,reasonable strength and toughness,and excellent plastic deformation resistance and multi-impact fatigue resistance are obtained by combined suitable ZrN gradient coating with plasma nitriding.The SPE resistance of the 2Cr13 martensite stainless steel substrate is significantly improved by the duplex surface treatment layer at 90° impingement angle.The SPE resistance of the ZrN gradient coatings is also related to the coating thickness.The thin ZrN gradient coatings have low SPE resistance because these coatings have poor coordinate deformation capacity and supporting capacity,meanwhile these coatings are easily detached from substrate under impact load.The thick ZrN gradient coatings also have low SPE resistance because these coatings have low toughness and poor adhesion strength and high residual stress,which easily result in these coatings local breaking off from the substrate under impact load.

Characterization of Plasma Electrolytic Carburized Stainless Steel in Glycerin Aqueous Solution

XUE Wen-bin, JIN Qian, ZHU Qing-zhen, WU Xiao-ling

2010, 30(4): 38-42.

[Abstract](1618) [PDF 564KB](338)

Abstract:
Rapid carburization on AISI 304 stainless steel was achieved by plasma electrolytic technique in glycerin + 20% water solution.The microstructure of carburizing layer was analyzed,and its tribological behaviors against GCr15 bearing steel ball under dry friction were evaluated using a SRV ball-on-disc friction tester.The results show that after 3 min and 350 V plasma electrolytic carburizing,the depth of carburizing layer is up to 85 μm and its maximum microhardness is 762 HV0.02.Under dry friction,the wear rate of carburizing layer against GCr15 bearing steel ball decreased about one order of magnitude compared to untreated AISI304 substrate.

Study of Flame Sprayed and Laser Remelted Al-Si Coatings on Magnesium Alloy

HAO Xin-ni, XU Xiao-jing, XIA Deng-fu, ZHUO Liu-cheng, ZONG Liang, WANG Hong-yu

2010, 30(4): 43-47.

[Abstract](1532) [PDF 1255KB](275)

Abstract:
Al-Si coatings on magnesium alloy substrate were prepared using flame spraying and laser-remelting technology.The microstructures and properties of the coatings before and after laser-remelting treatment were examined.The results show that the coatings prepared by merely flame spraying are not satisfactory coatings,with certain imperfections such as insufficiently dense microstructures and a lower hardness.After laser-remelting,a high quality coating was successfully developed.This coating presented many characterizations,such as dense and uniform microstructures,intensive element diffusion,good metallurgical bonding in interface,and a high hardness(HV270).Moreover,the laser-remelting treatment made the top in substrate along with the coating melted and inter-fused,leading to a considerable increase in coating thickness.It is believed that the compact microstructure of the coating can be ascribed to the chemical composition in the coating,which corresponds to a very narrow solidification temperature range,i.e.excellent castability.The present results demonstrate the possibility of preparing superior Al-Si thick coatings on magnesium alloy through flame spraying and laser-remelting approaches.

Investigation of Micro-droplets Forming on Surface of 7B04 Aluminum Alloy Deposited by Inorganic Salt

GUO Meng-qiu, CAI Jian-ping, LIU Ming, SUN Zhi-hua, ZHANG Xiao-yun

2010, 30(4): 48-52.

[Abstract](1461) [PDF 956KB](202)

Abstract:
The effect of NaCl,NaNO3 and Na2SO4 particles on the micro-droplet forming of aluminum surface was investigated using environmental scanning electron microscope(ESEM).The results show that the micro-droplets are easier to form on 7B04 aluminum alloy surface when there are inorganic salt particles,and results in atmosphere corrosion;the critical vapor pressure of micro-droplets forming increases while the critical relative humidity decreases for the same inorganic salt with raising temperature.In the research temperature range,the critical relative humidity of micro-droplets forming is lowest while NaCl particles deposite.The abilities of causing atmospheric corrosion(from strongest to weakest) are:NaCl,NaNO3,Na2SO4.

Salt Spray Corrosion of Ni/Graphite Abradable Sealing Coatings

XU Cun-guan, DU Ling-zhong, ZHANG Wei-gang, YANG Bin, WANG Lu, LI Ji

2010, 30(4): 53-58.

[Abstract](1573) [PDF 1025KB](327)

Abstract:
A systematic NiAl-Ni/Graphite abradable sealing coating for aircraft engine was prepared by thermal spraying technology.The corrosion property of the coating was studied in a salt spray cabinet to simulate the accelerated destroy in the ocean-atmosphere environment.The results show that the corrosion pretension of the coating in the oxygen-saturate and de-oxygen 5% NaCl solution(mass fraction)are-382.3 mV and-848.2mV,respectively.The major corrosion product after salt spray corrosion was a kind of amorphous Ni(OH)2·xH2O,and the graphite separated from the coating surface.The relationship between corrosion weight loss of the coating and corrosion time followed the power exponent function.The change of the bond strength of the coating was not obvious at the initial corrosion stage.However,the bond strength of the coating decreased rapidly after 480h,and it decreased about 30% after 960h.The corrosion mechanism of the coating in the salt spray cabinet was studied and the results show that the corrosion medium permeates the porous coating by capillary pressure.When the pores are filled with the medium,the medium exchanges between the surface and the interior are very difficult,which will lead to a macro-corrosion cell between the surface and the interior of the coating and accelerates the interior corrosion of the metallic connecter.

Relation between Pitting Corrosion Behavior and Exposed Area of High Strength Aluminum Alloys in Neutral Salt Spray

XU Huo-ping, LIU Hui-cong, ZHU Li-qun, LIU Jian-zhong, YE Xu-bin, HU Ben-run

2010, 30(4): 59-64.

[Abstract](1493) [PDF 1507KB](303)

Abstract:
The pitting corrosion characteristics of high strength aluminum alloys(2A12 and 7B04) with different exposed areas(simulating the destructive section of coatings or film on the aluminum alloy surface) by neutral salt spray test were investigated.The corrosion area,pitting depth and pitting quantity were measured.The results show that pitting corrosion of 2A12 and 7B04 aluminum alloys are accelerated with the increase of exposed area in the neutral salt spray test.The maximum corrosion area of aluminum alloys increases with the exposed areas when it is less than 25mm2;Moreover,the maximum pitting depth of 2A12 increases with exposed areas when it is less than 4mm2,while the maximum pitting depth of 7B04 increases with exposed areas when it is less than 100mm2.Component analysis of corrosion products indicates that the main components of corrosion products of 2A12 aluminum alloy are O,Al,Mg,Cu,while the corrosion products of 7B04 aluminum alloy are mainly O,Al,Mg,Zn.The different compositions of corrosion products causes their different structures,so that the pitting corrosion behavior of aluminum alloys is different.

Synthesis of Magnesium Hydroxide Platelets with Nano-Sized Thickness on Porous Magnesium Substrate by Hydrothermal Process under Atmospheric Pressure

LI Meng

2010, 30(4): 65-69.

[Abstract](1709) [PDF 1081KB](243)

Abstract:
Magnesium hydroxide(Mg(OH)2) platelets with nano-sized thickness have been synthesized on a sintered porous magnesium substrate by an open hydrothermal process under atmospheric pressure.Morphology and phase evolutions of the substrate during the reaction were investigated using scanning electron microscope(SEM) and X-ray diffraction(XRD).The nucleation and crystal growth mechanism of the nano-sized Mg(OH)2 platelets during the hydrothermal process are discussed as well.The results show that the pores among the sintered particles on the Mg substrate are the preferred areas to form the platelets.In addition,the shedding of Mg(OH)2 platelets from the substrate is carried out by ultrasonic treatment.The water absorption rate of the obtained Mg(OH)2 sample increases in the moist steam at 123℃ within a long time.

Modification Research of C/C Composites with Microwave Hydrothermal Method by Impregnating in H₃PO₄ Solution

MI Qun, CAO Li-yun, HUANG Jian-feng

2010, 30(4): 70-74.

[Abstract](1553) [PDF 742KB](178)

Abstract:
Carbon/carbon(C/C) composite was modified by a novel microwave hydrothermal treatment method using phosphoric acid solution as filling solution and modifier.The influences of microwave hydrothermal treatment temperature and time on the microstructure and oxidation resistance of the as-modified C/C composites were particularly investigated.Results show that the anti-oxidation of the material modified in phosphoric acid improves obviously.Microwave hydrothermal treatment is an effective process to improve the oxidation resistance of the C/C composites.The anti-oxidation property of the composites improves with increasing hydrothermal treatment temperature at the temperature range of 120~210℃.The oxidation resistance of the material is best after four hours hydrothermal treatment.The mass loss of the modified C/C composites is 9.47% after oxidation at 700℃ in air for 10h,which is much lower than the non-modified C/C composites.

Influence of Hygrothermal Environment on Absorption and Mechanical Properties of Advanced Composite T300/5405

LIU Jian-hua, CAO Dong, ZHANG Xiao-yun, LU Feng

2010, 30(4): 75-80.

[Abstract](1593) [PDF 1290KB](325)

Abstract:
The moisture absorption behaviors of uni-directional T300/5405 composite were studied in six kind of different hygrothermal environment.The morphology of the composites in the absorption processes was observed with SEM.The diffusivity in each environment was calculated.The shear strength,flexural strength and compression strength of the aging samples were measured.The results show that the diffusivity increases with the high temperature and humidity.Mechanical properties of the composites decline with the aging times,and the humidity in the same temperature makes the properties dropped faster.

Effects of Process Parameters upon Shear Modulus of X-cor Foam Sandwich Structure

CHEN Hai-huan, ZHANG Xiao-jing, WANG Hai

2010, 30(4): 81-87.

[Abstract](1638) [PDF 1406KB](256)

Abstract:
Effects of process parameters and material properties upon the shear modulus of X-cor sandwich were studied.Three effective spring coefficients simulating pin-end constraints were formulized through analyzing the detail restriction mechanism between face and pin,which were used to compute the shear modulus of X-cor sandwich.Effects of parameters including the inclination angle of pin,oblique angle in pin-end,insertion length of pin,diameter of pin,pin and foam properties on the shear modulus of X-cor sandwich were investigated.The prediction values are consistent with the experimental results exactly,which means the method predicting the shear modulus of X-cor sandwich is effective.Parametric results show that the shear modulus improve significantly through increasing the inclination angle of pin,axial modulus of pin or diameter of pin.Besides,the influences induced by the oblique angle in pin-end and inserting depth of pin are minor.In addition,neglecting the contribution of foam to shear modulus is illogical when the foam is stiff enough.

Application of NIR Reflectance Spectra in Quality Analysis of Epoxy Prepreg

LI Wei, CHEN Ping, ZHOU Xue-qiu, SUN Bao-lei, GAO Wei-jia

2010, 30(4): 88-91.

[Abstract](1585) [PDF 389KB](187)

Abstract:
A quick and non-destructive method using near-infrared(NIR)diffused reflectance spectroscopy was executed to determine the resin content and the volatile content of the epoxy prepreg.Partial least square(PLS) regression algorithm was used to build the calibration models.The optimum models were obtained by selecting different spectral pretreated methods and spectral ranges.The models have determination coefficients(R2) of 97.16 for the resin content and of 95.48 for the volatile content,respectively.The root mean square errors of calibration(RMSEC) are 0.564% and 0.202%,respectively.The root mean square errors of prediction(RMSEP) are 0.617% and 0.274%,respectively.For the predicted set,the paired t test results show that there is no significant difference between the near infrared method and the standard method.The NIR method is satisfied in the quality determination of epoxy prepreg.The results reveal that the NIR spectroscopy can be used as a useful tool for the quality control during the manufacture of prepreg.

Study on Fatigue Performance of 7075-T651 Aluminum Alloys

HAN Jian, DAI Qi-xun, ZHAO Yu-tao, LI Gui-rong

2010, 30(4): 92-96.

[Abstract](5235) [PDF 1067KB](1242)

Abstract:
The fatigue life experiments of 7075-T651 aluminum alloy were conducted under different stress amplitude and S-N curves was gained from fitting the experimental data.An estimation of detailed fatigue limit result was 223MPa.The fractography of high stress amplitude and low stress amplitude using scanning microscope displayed that the crack initiation mostly derived from the interior flaw or inclusion,and crack propagation gone with the quasi-cleavage crack.The crack propagation regions under high stress amplitude was characterized by furrow and tyre patterns while lots of fatigue fringe together with the fatigue sidestep and secondary crack generated in the crack propagation regions of low stress amplitude.The tearing edge and equiaxial dimples existed in fatigue failure region of both high stress amplitude and low stress amplitude fracture surface.The bulky inclusion particles can be the crack initiation while dispersion of tiny precipitated phase has a positive influence on fatigue performance of 7075-T651 aluminum alloy.

Study on Fatigue Fractography of High Strength and Toughness Aluminum Alloy for Aviation

JIAN Hai-gen, JIANG Feng, ZHENG Xiu-yuan, WEI Li-li, HUANG Hong-feng, WEN Kang

2010, 30(4): 97-102.

[Abstract](1785) [PDF 1364KB](422)

Abstract:
The fatigue fractography of 7B04-T7451 aluminum alloy was investigated by means of optical microscopy(OM),scanning electron microscope(SEM) and energy dispersive spectrometer(EDS).The micrographics show that the fracture surface is mainly divided into three zones such as the crack initiation,steady crack propagation and instantaneous fracture.Fatigue cracks mainly initiated at the Fe-rich intermetallic particles,which are about(7～10)μm×(11～14)μm in size and located at or near the specimen free surfaces.It also shows that fatigue cracks propagate radially.Some classical features exist in the fatigue propagation zone.The fracture morphology of the instantaneous fracture zone is similar to the one at static loading,which form a rough and uneven surface.

2010 Vol. 30, No. 4