航空材料学报

A Study of Damage Mechanical Behavior for Non-Metallic Inclusion in P/M FGH95 Superalloy

ZHOU Xiao-ming, WANG Dian-long, WANG Yu, WANG Xu-qing, WANG Wu-xiang, YAN Ming-gao

2008, 28(2): 1-4.

[Abstract](1496) [PDF 1045KB](197)

Abstract:
The distribution of stress field in non-metallic inclusion and matrix was simulated by the means of damage mechanical.And the simulation results were approved by in-situ tension experiment.The results show that tensile stress concentrates at the top of round inclusion from which the fracture initiates when the matrix is elastic,and then at the its equator from which the fracture propagates into the matrix while the matrix is elastic-tenacity;The fracture initiates at the top of the quadrate inclusion,and propagates into the matrix from its sharp corner.The simulation results are approved well by in-situ tension experiment,which indicates that the two stages,elastic-tenacity,should be used into the simulation.

MaximummSuperplasticity Deformation for TC11 Titanium Alloy

ZHAO Xiao-bin, WANG Gao-chao, CAO Chun-xiao, LI Zhen-xi, YANG Gang, FAN Ding-bing

2008, 28(2): 5-8.

[Abstract](1551) [PDF 1138KB](428)

Abstract:
The emphasis was placed on the experiment method and the computer control system of maximummsuperplasticity deformation(MaxmSPD).The superplastic deformation by this method for TC11 titanium alloy was analysed.The experiment results show that fine grain treatmemt TC11 titanium alloy,controlled by MaxmSPD,produces marked superplastic behaviour,in comparison with those constant strain rate methods.For example,at 900℃,the former elongation is 2300%,while the latter is only 1260%.The superplastic deformatiom of TC11 titanium alloy gives first place to grain boundaries slip,accompanied with grain intra dislocation slip.Maximummsuperplasticity deformation can amply occur dynamic recrystallization,it is also an efficacious way to improve deformatiom of titanium alloy.

Effects of Heat Treatment on Impact Toughness of Alloy GH2150A

ZHAO Yu-xin, YUAN Ying, MIAO Hong-bo

2008, 28(2): 9-13.

[Abstract](1400) [PDF 751KB](177)

Abstract:
The effect of microstructure changes after pre-treatment and intermediate heat treatment on the impact properties of room temperature of GH2150A alloy was researched.Optical metallography and SEM were used to observe the microstructure and impact fracture of the alloy.The results showed that,after the treatment,the impact toughness at room temperature was significantly improved.Compared with the standard heat treatment,Ak increased by 36%.The main reason for the improvment was that,it changed precipitation volume,shape and distribution of the carbide and decreased the size of γ′,so it changed the fracture mechanism of impact at room temperature.The treatment could obtain good comprehensive properties.

Effect of Hot-Die Forging on Interfacial Strength and Microstructure at Welded Seam of Ti-24Al-15Nb-1.5Mo/TC4 Dual Alloys

GAO Jun, YAO Ze-kun, LIANG Xin-min, LIU Ying-ying, GUO Hong-zhen

2008, 28(2): 14-18.

[Abstract](1486) [PDF 846KB](279)

Abstract:
The effect of hot-die forging on changing the micro-hardness distribution,trend of elements diffusion,microstructure and tensile property in the weld of Ti3Al-Ti dual alloys welded by electron beam in vacuum was investigated.The results show that the content of elements Al and Nb change abruptly in the boundary of the sample's joint not treated;The micro-hardness of the sample treated by 700℃×12h,AC is the highest,and average HV0.98 is up to 3780 MPa.By hot-die forging and heat-treating,elements fully diffuse,microstructure and micro-hardness distribution is uniform.The results of tensile test for welding joints show that the sample deformed by 38% in 1020℃ and treated by 700℃×12h,AC has the best mechanical property with 16.5% elongation and 44.5% reduction of area,and its microstructure is two-state structure.

Joining of Titanium Alloy/Nb/Stainless Steel using TIG Welding and Brazing Methods

YE Lei, XIONG Hua-ping, LI Xiao-hong, MAO Wei, CHENG Yao-yong

2008, 28(2): 19-23.

[Abstract](1622) [PDF 1733KB](235)

Abstract:
The wettability of AgCu-1.8Ti and AgCu-4.4Ti brazing fillers on Nb and 0Cr17Ni4Cu4Nb stainless steel was studied with sessile drop method.The result showed that the both contact angles of AgCu-1.8Ti on Nb and 0Cr17Ni4Cu4Nb were less than those of AgCu-4.4Ti.A Ti-rich layer about 50μm wide was found in the joint of Nb and 0Cr17Ni4Cu4Nb with AgCu-4.4Ti brazing filler.However,when using AgCu-1.8Ti brazing filler,no such Ti-rich layer was found.The room-temperature tensile strength of TC4/Nb/0Cr17Ni4Cu4Nb joint was tested.Firstly,TC4 and Nb was joined by TIG welding,and then TC4/Nb joint was brazed to 0Cr17Ni4Cu4Nb with AgCu-1.8Ti and AgCu-4.4Ti brazing fillers respectively.The average strength of the joint with AgCu-1.8Ti reached 222.2MPa,but for AgCu-4.4Ti,it was only 133.8 MPa.All the tensile samples were fractured at the interface of Nb and 0Cr17Ni4Cu4Nb.

Experimental Analysis on Compressive Residual Stress Distribution Induced by High Speed Face-Milling Processes

LONG Zhen-hai, ZHAO Wen-xiang, WANG Xi-bin

2008, 28(2): 24-29.

[Abstract](1438) [PDF 1165KB](234)

Abstract:
The residual stress distribution beneath wokepiece surfaces machined by high speed milling process was investigated,tests of face milling were conducted in the frame of a factorial design and X-ray diffraction analysis of specimens was performed to obtain the residual stress distribution by electro-polishing method.The influences of cutting parameters on characteristics of the compressive stress distribution were studied according the regression predictive models fitting from residual stress distributions measured in tests.It is shown that high speed milling can induce a compressive stress distribution below the machined surface.A Cubic/Linear rational model and a third-degree polynomial model are effective for fitting of the compressive stress distribution.The level of compressive residual stresses depends on the cutting parameters used in tests and feed per tooth is the decisive factor on the residual stresses distribution.

Computer Simulation on Process of Multi-Crack Initiation

HUANG Xin-yue, Angelika Brueckner-Foit

2008, 28(2): 30-33,49.

[Abstract](1465) [PDF 1001KB](167)

Abstract:
A two-dimensional computer simulation on the process of multi-crack initiation was described.The damage accumulation was presented by the crack density per unit area.The number of cycles to crack nucleation was estimated by the Tanaka-Mura equation.The model simulated the microstructural parameters influences(such as grain size and orientation) on fatigue life.A quantitative prediction was obtained.The model was applied to simulate the multi-crack initiation in a martensitic steel F82H.The results from simulation coincided with experimental data quite well.

Growth and Characterization of Microarc Oxidation Film on LC4 Aluminum Alloy

XUE Wen-bin, HUA Ming, DU Jian-cheng, TIAN Hua, SHI Xiu-ling

2008, 28(2): 34-38.

[Abstract](1479) [PDF 639KB](378)

Abstract:
The growth kinetics of microarc oxidation(MAO) films on LC4 Al-Zn-Mg-Cu alloy was investigated and the geometrical dimension change with oxidation time was determined.The microstructure,composition and phase component of film were analyzed,its microhardness profile was measured and the electrochemical behavior of films before and after MAO treatment thickness were evaluated.In the initial oxidation stage,the current density was high and film growth was fast.After it began a stable growth,the current density reduced to a stable value and growth rate decreased.The film was composed of γ-Al2O3,α-Al2O3 and amorphous SiO2,and the relative content of γ-Al2O3 phase was rather high.The microhardness of film was much high than the LC4 aluminum alloy;its average hardness in inner layer and outer layer was about 1600 HV and 450 HV,respectively.By MAO surface treatment,the corrosion current of LC4 alloy was significantly reduced and its corrosion resistance was greatly improved.

Corrosion Behaviors of Aluminum Alloys in Simulated SO₂ Pollute Atmosphere

ZHOU He-rong, LI Xiao-gang, DONG Chao-fang, XIAO Kui

2008, 28(2): 39-45.

[Abstract](1432) [PDF 2043KB](448)

Abstract:
The corrosion behaviors of aluminum alloys 1060,2A12 and 7A04 in two different experimental conditions were investigated by scanning electron microscope(SEM),energy dispersive X-ray detection(EDX),Fourier transform infrared(FTIR),X-ray diffraction(XRD) and mass gain method in simulated 50ppm SO2 pollute atmosphere.The mechanical capability of experimental materials under different corrosion time was tested.The results show that the corrosion product increases with testing hours prolonging,mass gain of corrosion product adding and according with exponential attenuation rule as Δm/A=B+Dexp(-t/k),strength and elongation percentage declining.Surface observation showed that corrosion product was agglomerate and accidented,extending forth.The corrosion product of aluminum alloys in simulated 50ppm SO2 atmosphere was little and composed of alumina and aluminum sulfate.But the corrosion product of aluminum alloys on the surface of 70μg·cm-2 sodium chloride was more in simulated 50ppm SO2 atmosphere,mass gain of corrosion product adding more,strength and elongation percentage declining more greatly,corrosion product made up of alumina,aluminum sulfate hydrate and aluminum chloride.

Influences of Fibre Surface Coatings on Properties of Carbon Fiber/Polyarylacrtylene Composites

WANG Tian-yu, HUANG Yu-dong, CAO Zheng-hua, LIANG Xian-zhu

2008, 28(2): 46-49.

[Abstract](1376) [PDF 325KB](246)

Abstract:
Different kinds of coatings,including epoxy,siloxanes,and silsesquioxanes,were used to modify carbon fibres(CF) surface in order to improve the properties of carbon fibre/polyarylacetylene(CF/PAA) composites.Short-beam bending and heat oxygen aging tests of composites were carried out to characterize the effects of different coating treatments.Interlaminar shear strength(ILSS) of treated composites showed that the silsesquioxane had the best treating effects.Heat oxygen aging tests suggested that silsesquioxane fit to be used in heat resistant resin system.This kind of treating method could be used in all kinds of resin system by changing the functional groups on silsesquioxane according to those on resin.

Microstructure Study of the SiC Coatings on Graphite by CVD

HUANG Hao, CHEN Da-ming, TONG Jian-feng, LI Bao-wei

2008, 28(2): 50-54.

[Abstract](1575) [PDF 1444KB](452)

Abstract:
The SiC coating by CVD process on graphite was studied by scanning electron microscope(SEM) in CH3SiCl3-H2-Ar system.The influence of temperature,the proportion and flow rate of carrier gas and dilute gas on the microstructure of CVD SiC coating were investigated.The experimental results show that the optimum condition for the SiC coating are at 1100℃,H2:MTS=5:3,total gas flow rates 8L/min,diluent flow rates 1L/min.A dense and smooth coating will be obtained.The reaction temperature is the most sensitive factor to the morphology of coatings.The CVD SiC coatings are dense and smooth at the reaction temperatures at 1100℃.

Numerical Simulation of Residual Strain/Stress for Composite Laminate during Overall Curing Process

HU Zhao-hui, WANG Rong-guo, HE Xiao-dong, DU Shan-yi

2008, 28(2): 55-59.

[Abstract](1169) [PDF 443KB](369)

Abstract:
The process induced residual strain/stress of composite laminated plate with aluminum plate was numerically simulated by commerce software.Finite element analysis was used to simulate thermal-chemical model of composites laminated plate,and finite difference method was employed to calculate its cure kinetics model during curing process.The strong coupled relation between cure kinetics model and thermal-chemical model was expected to consider by setting minionum time step in finite difference method.Chemical shrinkage was applied to composite materials as an initial strain for each time increment in residual stress simulation residual strain/stress of composite laminated plate with aluminum plate was successfully simulated on the basis of the mentioned technology.Moreover,history of residual strain/stress at along fiber orientation and vertical fiber orientation of composite material were analyzed.Compared to deflection of laminate in test,the validity of the results calculated by model was proved.

Influence of Aluminium Content on Oxidation Behavior of Particle Reinforcing Titanium Matrix Composites

WANG Hui-gai, ZHANG Yong-zhen, WANG Fei, WEI Zun-jie

2008, 28(2): 60-64.

[Abstract](1401) [PDF 1600KB](243)

Abstract:
With the reaction between titanium(Ti) sponge,high purity aluminum(Al) and TiC/Al interalloy,non-consumable arc melting technique was successfully used in situ synthesize Ti matrix composites with different Al contents.The isothermal oxidation behavior of composites at 800℃ and 900℃ in air was investigated.The effect of different Al contents on composites was analyzed.The surface morphology and cross-section microstructure of the oxidation scale were examined by scanning electron microscope(SEM) with energy dispersive spectrometer(EDS).The results show that the isothermal oxidation kinetic curves of composites mainly follow parabolic rate law.The oxidation resistance of composites increases with increasing Al content to a certain extent.Oxides of Al increase and oxides of Ti decrease.

Research on Meso-Scale Damage Fracture and Series-to-Parallel Failure Model for SiCp/A356 Composites

YANG Zhi-yong, HAN Jian-min, LI Wei-jing, WANG Jin-hua

2008, 28(2): 65-69,90.

[Abstract](1529) [PDF 1496KB](238)

Abstract:
The meso-scale damage fracture mechanism of silicon carbide(SiC) particulate reinforced aluminum matrix composite specimens from the SiCp/A356 brake disk products was investigated on the room and high temperature.Fatigue crack initiation and propa-gation behaviors were examined by using an S-250MK3 scanning electron microscope on the fractured surfaces.It was also found that the crack growth rate was decreased due to the hindering effect of the particles or the change of the growth plane of the cracks,and the striations radiating from SiC particulates could be shown.A series-to-parallel model of micro-damage was proposed in order to explain the initiation and propagation of cracks.It is concluded that the damage evolution could be expressed in a series-to-parallel model of micro-damage.

Nonlinear Constitutive Relation for Metal-Rubber with Different Density

LI Yu-yan, HUANG Xie-qing

2008, 28(2): 70-75.

[Abstract](1485) [PDF 412KB](336)

Abstract:
On the basis of theory of porous material and dry friction,and combining with the model of small curved beam,nonlinear constitutive relation of metal-rubber was constructed.Static compressive experiments were made for hollow cylinders of metal-rubber.Experimental data were sorted out for curve fitting,then relations between all the coefficients in constitutive relation and the density of the material were obtained.Eventually constitutive relation of the material was predicted successfully.

Synthesis and Property of Fluorenylidene-Containing High Temperature Resistant Polyimides

LIU Jin-gang, CHEN Jian-sheng, YANG Hai-xia, YANG Shi-yong

2008, 28(2): 76-81.

[Abstract](1545) [PDF 1747KB](373)

Abstract:
An aromatic diamine with ether linkage and fluorenylidene moiety,9,9-bis(4-aminophenoxyphenyl)fluorene(BAOFL) was synthesized with high purity,which could be confirmed by melting point,FT-IR and NMR measurements.Two polyimides(PIs) were prepared by polymerizing the diamine with 3,3′,4,4′-biphenyltetracarboxylic dianhydride(sBPDA) and 2,3,3′,4′-biphenyltetracarboxylic dianhydride(aBPDA),respectively by thermal imidization or chemical imidization procedure.The effects of fluorenylidene moiety on the thermal property,solubility,and optical property were investigated.It was found that the fluorenylidene-containing PIs had good solubility in common solvents and good optical transparency in the visible light region.In addition,the PIs exhibited good thermal stability with the glass transition temperatures of higher than 280℃ and initial thermal decomposition temperatures of higher than 500℃ in nitrogen.

Study on Properties of Phenol Type Epoxy Resin Modified by Bismaleimide

LI Quan-bu, HU Cheng-yao, YE Wei, GU He-ping, HUANG Pei

2008, 28(2): 82-86.

[Abstract](1534) [PDF 623KB](501)

Abstract:
The system of phenol type epoxy resin(F-51) /amine(DAMI) modified by bismaleimide(BMI) were studied.The cured materials were characterized using differential scanning calorimetry(DSC),thermogravimetric analysis(TGA) and thermomechanical analysis(TMA).DSC thermograms showed the BMI improved the peak maximum temperatures with reduction in the total energy of heat source.Thermal studies indicated that BMI enhanced the thermal stability.The mechanical properties were investigated with GB standards.The results showed that the introduction of BMI into epoxy resin improved the mechanical properties.SEM observation of the fracture of the tensile specimen showed that the toughened fracture characters were obviously appeared for the blends.

Research on Complex Permittivity Spectrum and Microwave Absorption of Anti-Infrared In(Sn)₂O₃(ITO) Painting

ZENG Guo-xun, ZHANG Hai-yan, HU Li-chu, CHEN Yi-ming

2008, 28(2): 87-90.

[Abstract](1700) [PDF 1565KB](349)

Abstract:
The permittivity of 7.7vol% and 15.8vol% ITO/wax composites were measured in the frequency of 2～18GHz,respectively.The results revealed that ITO had good dielectric property.Reflection loss of-10.5dB and-14dB were obtained at 4.51GHz and 6.27GHz for ITO/Epoxy resin samples of 20vol% and 10vol%,respectively.The theoretical values of 15.8vol% ITO / wax composite exhibited good microwave absorption property(reflection loss -10dB) in the frequency rang of 4.56~11GHz,with thickness of 3mm.The dielectric loss mechanism of ITO was analyzed.

Pyrolysis Study of Phenolic Formaldehyde Resin at High Temperature by Shock Tube Test

MA Wei, WANG Su, FAN Bing-cheng, HE Yu-zhong, ZHANG Sheng-tao, CUI Ji-ping

2008, 28(2): 91-94.

[Abstract](1467) [PDF 396KB](256)

Abstract:
The pyrolysis behavior of phenolic formaldehyde resin was studied in a shock tube at high temperatures between 1200K and 1800K.The major hydrocarbon products were identified as methane,ethene,acetylene,benzene and toluene.The variation of the major products distribution with pyrolysis temperature was obtained.It was found that the thermal decomposition of phenolic formaldehyde resin mainly took place at the methylene bridges at the temperatures below 1400K,while the cracking of aromatic framework became the major pyrolysis pathway at the temperatures above 1400K,which gave birth to large amount of acetylene.

Computer Geometry Simulation of Spatial Structure of Three-Dimensional Braided Composites

WANG Yi-qiang, ZHANG Li-tong, CHENG Lai-fei

2008, 28(2): 95-98.

[Abstract](1617) [PDF 991KB](237)

Abstract:
For 4-step square braiding structures,a representative geometric model of unit cell was presented through studying the actual braiding process,as well as fabrics spatial geometry model.It is composed of a series of yarns,the structure of which is formed when yarn carriers wind a full cycle and return back to the initial start position,such a model ensures continuity of yarn bunches and integrity of braided composite structure.For each yarn,control points were assigned properly in all regions of braided volume,then the cubic B-spline curves were constructed by passing these control points,forming the central axes of yarn spatial structure.Finally the structure of yarns and the braided cell was generated,which was quite suitable for the next FEM analysis of the mechanical properties of the braided composites.

2008 Vol. 28, No. 2