航空材料学报

Study on In-Plane Anisotropy of 2524 Aluminum Alloy Sheet

GUO Jia-lin, YIN Zhi-min, SHANG Bao-chuan, NIE Bo, HE Zhen-bo

2009, 29(1): 1-6.

[Abstract](4366) [PDF 676KB](1202)

Abstract:
The microstructures and tensile properties of cold-rolled and T3 treated 2524 aluminum alloy sheet with the thickness of 2mm at different orientation were investigated by tensile test,OM,XRD and TEM analysis.On the basis of the model that regards the sheet containing only {110}texture,the relationship of in-plane anisotropy and the anisotropy of crystallography was analyzed.The results show that the strength of 2524 cold-rolled and T3 sheet orientated 45° and 60° with respect to the rolling direction is lower than that of specimens orientated 0°,30° and 90° with respect to the rolling direction.The elongation of the sheet orientated 45° with respect to the rolling direction is highest,And then the tensile properties of the sheet orientated 0° with respect to the rolling direction are both higher than that of the sheet orientated 90° with respect to the rolling direction.The IPA of cold-rolling condition alloy sheet is higher than that of T3 condition.The major crystallographic texture of 2524 cold-rolled sheet is {110},and the secondary crystallographic texture is {311}.But the major crystallographic texture of 2524-T3 condition is {110}.The in-plane anisotropy of mechanical properties of 2524 aluminum alloy sheet is closely related to the grain structure and crystallography orientation,among them crystallographic texture is responsible for the in-plane anisotropy of mechanical properties.

Influence of Vibratory Stress Relief on Two-way Memory Strain of NiTi Shape Memory Alloy

WANG Zhi-gang, JIANG Da-qiang, CUI Li-shan

2009, 29(1): 7-10.

[Abstract](1226) [PDF 809KB](160)

Abstract:
The influence of vibratory stress relief on two-way memory strain of NiTi shape memory alloy was investigated.The results indicated that the two-way memory strain was increased when the vibration was imposed on the NiTi alloy with smaller and larger prestrain,while the strain was decreased when the vibration was applied to the NiTi alloy with moderate prestrain.This could be caused by microscopic plastic deformation during vibration.

Stacking Fault Energy and Effect Factors of Ni-Al-Ta/Mo Alloys

YU Xing-fu, TIAN Su-gui, LU Xu-dong, SHANG Li-juan, WANG Tie-jun, MENG Hui, CUI Shu-sen

2009, 29(1): 11-15.

[Abstract](1204) [PDF 502KB](199)

Abstract:
Using the thermodynamic model of the substituting atoms,the stacking fault energy(SFE)of Ni-Al-Ta/Mo alloys has been calculated,and the influences of the elements and temperatures on SFE of Ni-Al-Ta(Mo)alloys have been analyzed.Results show that the SFE of Ni-Al-Ta /Mo alloys decreases obviously with the increase of Al concentration,thereinto,the fact that the accumulated Gibbs free energy(ΔGsγ→ε)decreases with the increase of the Al concentration promotes the accumulation of the Al atoms to form the γ'-Ni3Al order phase with Ll2 structure,which is a main reason for reducing SFE of Ni-Al-Ta/Mo alloys.The fact that enhances the concentration of the elements Ta/Mo decreases the replacing Gibbs free energy(ΔGbγ→ε)of atoms,and increases the accumulated Gibbs free energy(ΔGsγ→ε)of atoms.With the elevated temperature,the increment of ΔGbγ→ε shows that the atoms replacing occurred in the alloy needs supplying energy by environment,and the increment of ΔGsγ→εshows that the atomic accumulation is not easily occurred in high temperature.

Fabrication of High Nb Containing TiAl Alloys by High-Energy Ball Milling and Pressureless Sintering

LU Xin, HE Xin-bo, QU Xuan-hui

2009, 29(1): 16-21.

[Abstract](1265) [PDF 1598KB](183)

Abstract:
High Nb containing TiAl alloys were prepared by high-energy ball milling and pressureless sintering from Ti-45Al-9(Nb,B,W,Y)prealloyed powder with big particle size.The results showed that the compactibility and sintering densification of the prealloyed powder could be promoted efficiently by high-energy ball milling.After the prealloyed powder was milled for 60 minutes and subsequently sintered at 1500℃ for 2 hours,high Nb containing TiAl alloys with high density and fine fully lamellar microstructure could be obtained and were found to have good temperature mechanical properties with the compressive strength of 3150MPa and the relative compressive ratio of 25.2%.

Effect of α Grain Size on Deformation Behaviors of TC4 Titanium Alloy with Equiaxed Microstructure

CHENG Ming, ZHAO Jian-guo, SONG Hong-wu, ZHANG Shi-hong

2009, 29(1): 22-26.

[Abstract](1298) [PDF 639KB](255)

Abstract:
The deformation mechanism of TC4 alloy with different initial α sizes of 6μm,12μm,20μm respectively has been investigated by isothermal compression tests in a temperatures range 890~950℃ and strain rates range 0.1~10s-1.The results show that the effect of initial α size on flow stress is complicated and less significant compared to strain rate and temperature.Microstructure characterization and kinetic analysis show that the thermal activated deformation process of TC4 alloy is controlled by both phase transformation and grain growth.The calculated activation energy is much higher than the results reported.Small initial α size tends to aggregate and grow with a coarse grain size after deformation.With an initial α size of 12μm,phase transformation is improved and fine grain size is obtained after deformation.With initial α size increased to 20μm,slightly effect on grain size happened.

Evolution of Nd-rich Second Phase Particles During Electron Beam Welding and Its Effect on Tensile Fracture Behavior of Nd-Containing Titanium Alloy

CAI Jian-ming, YUAN Hong, LI Zhen-xi, HUANG Xu, MA Ji-min, CAO Chun-xiao

2009, 29(1): 27-31.

[Abstract](1211) [PDF 684KB](158)

Abstract:
Evolution of Nd-rich second phase particles during electron beam welding of Ti60 titanium alloy containing rare earth Nd and its effect on room temperature tensile fracture behavior have been studied using optical microscopy(OM)and scanning electron microscopy(SEM).After rapid melting and solidification of the welding joint during the electron beam welding procedure,the dispersed distributed Nd-rich second phase particles with about 10μm in Ti60 titanium alloy disc forging dissolved,nucleated and re-precipitated,the new formed Nd-rich second phase particles were refined to about 0.3μm,and were intermittently layer distributed parallel to the solidification direction.The welding joint and the interface between welding joint and heat affected zone show evident characteristic of intergranular brittle rupture.

Electron Beam Vapor Deposited La₂Zr₂O₇ Thermal Barrier Coaings

MU Ren-de, XU Zhen-hua, HE Shi-mei, HE Li-min

2009, 29(1): 32-36.

[Abstract](1395) [PDF 1377KB](254)

Abstract:
To improve the sufficiency of common used Y2O3 partly stabilized zirconia(YSZ)in heat resistant and thermal insulation properties,pyrochlore compound La2Zr2O7 was synthesized by air sintering of ZrO2 and La2O3.As top coating material of thermal barrier coatings(TBCs),the compound was evaporated and deposited on super alloy substrate by EB-PVD.The composition,microstructures and thermo physical properties of the coating were investigated and compared with its YSZ counterpart.Our results show that the composition of La2Zr2O7 coating in this study range over pyrochlore structure,the crystal of the coating presents typical columnar characteristic.The head of each columnar crystal appears clear pyramid shape.In comparison of YSZ,the columnar crystals of La2Zr2O7 coating are thinner,more disordered and have more dendritic sub grains.within 25～1200℃,the maximum thermal conductivity of La2Zr2O7 coating is 0.985W/(m·K)and the minimum is 0.796 W/(m·K),which are greatly lower than YSZ coating at the same conditions.Apparently,low inherent thermal conductivity,small columnar crystal diameter,chaos,light density and high cavity rate are main factors responsible for the low thermal conductivity of La2Zr2O7 coating.

Hot Deformation Globularization Kinetic Processes of TC11 Titanium Alloy with Lamellar Structure

CHEN Hui-qin, CAO Chun-xiao, GUO Ling, LIN Hai

2009, 29(1): 37-42.

[Abstract](1254) [PDF 775KB](232)

Abstract:
Hot deformation processes of TC11 with β-annealed lamellar structure were investigated over the range of temperature 980℃,950℃,800℃,strain rate 0.001 s-1 and 0.1s-1,and reduction from 30% to 70% by hot compression tests.The effects of thermal-mechanical parameters on deformation behavior and globularization processes were analyzed.According to the characteristic of globularization fraction evolution,a modified Avrami globularized kinetic model was established,which is identical to test data well.

Research on Dynamic Recrystallization Behavior of Directionally Solidified DZ4 Superalloy

JIA Bo, LI Chun-guang, LI Yun-ju, TAO Chun-hu

2009, 29(1): 43-46.

[Abstract](1208) [PDF 1005KB](205)

Abstract:
Research on dynamic recrystallization behavior of directionally solidified DZ4 superalloy bearing static tensile stress at high temperature was carried out.How the factors affect dynamic recrystallization behavior of DZ4 superalloy,including temperature,stress and surface oxidation is mainly researched.The results show that dynamic recrystallization will occur in oxide layer at surface of DZ4 specimens without coating at 800℃ to 950℃ and the depth of recrystallization zone increases with the increase of temperature and stress.Analysis shows that surface oxidation is main reason for surface dynamic recrystallization.Experiment results also show that dynamic recrystallization won't occur at surface of DZ4 superalloy blades with protective Al-Si coating at normal working conditions.

Effect of Ageing Time on Mechanical Properties and Microstructures of ZL210A Casting Aluminum Alloy

JIA Pan-jiang, CHEN Bang-feng

2009, 29(1): 47-50.

[Abstract](1285) [PDF 1449KB](329)

Abstract:
The study was on the effect of different ageing time on the mechanical properties,microstructures and fracture surfaces of the ZL210A casting Al alloy at 170℃ ageing temperature.The result shows that the tensile strength,yield strength and hardness of the alloy reach the maximum 500MPa,435MPa and 150HBs,respectively,while the elongation reaches the minimum 5% for 4h ageing time,and after that to remain constant with increasing ageing time.The ageing time has a big effect on the microstructures,which the transition is G.P.I→G.P.II(θ")→θ'→θ.The effect of ageing time on the fracture surface is little,and the fracture surfaces show excellent toughness.

Optimization of General Constitutive Equation for Hot Deformation of SiC Particle Reinforced Al Matrix Composites

ZHANG Peng, LI Fu-guo, LI Hui-qu

2009, 29(1): 51-56.

[Abstract](1172) [PDF 884KB](258)

Abstract:
Deformation behavior of SiC particle reinforced Al matrix composites has been investigated through the hot compression test carried out in the temperature 713~773K and strain rate 0.001~1s-1.Based on the experimental data and Zener-Hollomon parameter,the constitutive equation is modeled and discussed.Through the analysis,the constitutive equation is further optimized.As a result,the new optimization equation can improve the validity of application.

Microstructures and Mechanical Properities of Diffusion Bonded Ti₂AlNb and GH4169 Jionts by Using Nb+Ni Interlayer

QIAN Jin-wen, LI Jing-long, HOU Jin-bao, XIONG Jiang-tao, ZHANG Fu-sheng, HAN Zeng-chan

2009, 29(1): 57-62.

[Abstract](1278) [PDF 1480KB](339)

Abstract:
Vacuum diffusion bonding of Ti2AlNb and GH4169,by inserting metal foils of Ni+Nb as interlayer,was studied experimentally under the conditions of bonding temperature 950~1100℃,axial pressure 20MPa and holding time 20-120min.The joints microstructures and bonding mechanism were studied by SEM and EDS analyses.The results show that Ti2AlNb and GH4169 could be well bonded with metal foils of Ni+Nb as interlayer.There were six reacted layers between Ti2AlNb and GH4169,and the layers were Fe-Ni-Cr solid solution,Ni3Nb,Ni6Nb7,residual Nb,Ti-Nb solid solution,O phase with high Nb,orderly,from the GH4169.When sheared,the joint fractured in the Ni6Nb7 layer which between the Ni3Nb layer and the residual Nb layer.The maximum shear strength was 460.3MPa at 1050℃,20MPa,40min.

Microstructure and Performance of Laser Cladding on Surface of Aluminum Bronze

XU Jian-lin, YANG Bo, GAO Wei, WANG Zhi-ping, LONG Da-wei, JU Chun-yan, YU Tao

2009, 29(1): 63-67.

[Abstract](1151) [PDF 1264KB](258)

Abstract:
A Ni matrix alloy cladding was deposited on the surface of QAl9-4 aluminum bronze by laser remelted technology to improve its wear resistance.In order to improve absorptivity of aluminum bronze for laser irradiation,some alloy powders were pre-deposited on the surface of QAl9-4 aluminum bronze by compressive equipment and some binder,which was developed by researcher.Then,these alloy powders were remelted by laser.The analysis of the laser cladding on the surface of QAl9-4 aluminum bronze shows that the composite region of remelted cladding and QAl9-4 aluminum bronze is a better metallurgical bond and there aren't cracks.The microstructure of cladding is affected by solidification rate.The microstructure of the cladding's surface is cellulated crystal.In the middle part of the cladding,the microstructure is dendritic crystal.Because of chilling effect of QAl9-4 aluminum bronze,the microstructure of the composite region upper is fine grain band.The microstructure of the composite region lower is cellulated crystal and dendritic crystal.The average Vickers hardness of the cladding is three times as hard as that of ordinary QAl9-4 aluminum bronze.

Preparation and Mechanical Properties of Silicon Carbide Whisker Reinforced Silicon Carbide Mini Composites

WANG Jing, ZHANG Li-tong, CHENG Lai-fei, HUA Yun-feng

2009, 29(1): 68-71.

[Abstract](1192) [PDF 417KB](209)

Abstract:
Silicon carbide whisker reinforced silicon carbide mini composites were prepared by Chemical vapor infiltration(CVI),and the microstructure and mechanical properties were studied.The results show that the volume percent of whisker in the composites can reach 45%~50%,The average value of Vickers-hardness and the fracture toughness of the composites can reach 19.04GPa and 6.72 MP·m1/2,respectively.there are some toughening mechanism such as whisker bridge,whisker rupture,pull out,crack deflection which are produced by the incorporation of SiCW.The preparation of SiCW/SiC mini laid the foundation for subsequent fabrication of SiCW/SiC composites.

Processability of M-3193 Unsaturated Resins for Resin Transfer Moulding

HE Zhou-wen, CHENG Lai-fei, ZHANG Li-tong

2009, 29(1): 72-76.

[Abstract](1124) [PDF 684KB](218)

Abstract:
In this paper the processing property of M-3193 unsaturated polyester resin for Resin Transfer Molding is studied systematically.The effect of temperature,edge effect and SiC nm filler on resin liquidity and mechanical property of materials is analyzed.It is demonstrated that system of M-3193 unsaturated polyester resin maintains a viscosity well under 60mPa·s when the temperature is above 80℃ and large edge effect induces resin flow inadequate in fiber bundle,which reduced strength of composites.Besides,the hardness of composites increased 30%,and the strength of composites have no change when SiC nm filler is added.In another hand,the strength of composites is enhanced when perform is vacuum impregnated,the flexural strength of composites reach 325MPa.

Preparation of Anti-ablation HfC Coating on C/C Composite Material

HOU Gen-liang, SU Xun-jia, WANG Yan-bin, ZHOU Xiao-bo

2009, 29(1): 77-80.

[Abstract](1249) [PDF 590KB](279)

Abstract:
Anti-ablation HfC coating was prepared by liquid precursor conversion on the C/C composite material.The solution-derived precursor was studied by FT-IR.The HfC coating was characterized by XRD,SEM and EDS.The results showed the Hf-O-Hf and Hf-O-C bonds appeared in the solution-derived precursor.The coating was conversed into the HfC coating after heat treatment at 1800℃.The components of the coating were mostly HfC and HfO2.The C/C composite material was not covered with Single coating.The HfC coating was compact from multi-films.The thickness of the coating was about several tens micron.The interface was not obvious.The transition coating between body and coating can relax interface stress and improve integrate intensity.

Influence of TiO₂ Nano Particles on Properties of Nanofiber Reinforced Transparent Composites

CHEN Lu-song, HUANG Zheng-ming, XUE Cong

2009, 29(1): 81-86.

[Abstract](1219) [PDF 1466KB](215)

Abstract:
Development of nanofiber reinforced transparent composites added with nano-titanium dioxide(TiO2)particles was made in this paper,in which poly(methyl methacrylate)(PMMA)acted as the matrix material.Applying the same amount of TiO2 particles either in core or in shell part of co-axially electrospun composite nanofibers,their distribution status in different parts and their influence on optical properties of the transparent composites such as visible light transparency and ultraviolet light absorbency was analyzed.Results show that the added TiO2 particles in the core part gave less influence on the visible light transparency,accompanied with an obvious absorbing peak in ultraviolet light region around wavelength of 200~400nm-1.

Acoustic Impedance Matching Criteria and Their Applications for Layer Thickness Measurement by Ultrasonic Interferometry

CHEN Xiu-ming, LIN Li, LI Xi-meng, GUO Guang-ping

2009, 29(1): 87-91.

[Abstract](1211) [PDF 477KB](273)

Abstract:
Based on the fundamental principles of ultrasonic interferometry of thin layer thickness measurement,criteria are proposed when the interfacial reflection coefficient between the layer and its adjacent medium meets |R1|2or |R1|>1/√2,respectively.And a choice between the minima and maxima used in thickness measurement is made by investigating secondary extreme of the reflection coefficient spectrum under two conditions.Using the above principles,the thickness of Airborne Radome Skin coating and ZrO2 ceramic coating sprayed on steel substrate are experimentally studied.Comparing with the SEM(Scanning Electron Microscope)results,the experimental error ε1≤12% for Airborne Radome Skin coating and ε2≤11% for ZrO2 ceramic coating,both meet the need of engineering.It is concluded that the acoustic impedance matching criteria are of great value in layer thickness measurement using ultrasonic interferometry.

Fabrication and Photoluminescence Study on ZnO Nanostructured Particles

CHENG Xing-wang, LI Xiang, ZHAI Fei-fei, YU Zhou, LONG Xue, LIN Peng-ting

2009, 29(1): 92-95.

[Abstract](1155) [PDF 1038KB](298)

Abstract:
Uniform and compact ZnO nano-particles were synthesized on Si substrate via a polymer capping method.The morphology and optical property of as-synthesized samples were characterized by SEM,AFM and PL spectra.It was observed that pH value of the precursor had a great effect on the dispersibility and size of the nano-particles,which further induced a change of the peak position of the PL spectra in ultraviolet range.In detail,experiment results indicated that the PL spectra peaks in ultraviolet range had a red-shift as the size of nano-particles increased,conforming to the quantum size effects.

Study on Fatigue Performance of High Strength Aluminum Alloy

DU Feng-shan, YAN Liang, DAI Sheng-long, YANG Shou-jie

2009, 29(1): 96-100.

[Abstract](1130) [PDF 1314KB](443)

Abstract:
High cycle fatigue of 2E12 aluminum alloy was investigated under different stress ratio and stress concentration factor at room temperature,and fracture mechanism was discussed.The microstructures and fatigue fracture surfaces of the alloy were examined by transmission electron microscopy and scanning electron microscopy.The results showed that the fatigue life of 2E12 aluminum alloy improves with increasing of stress ratio and the fatigue life of Kt=1 was longer than that of Kt=3,exhibiting notch sensitivity.The fatigue fracture consisted of fatigue crack source,fatigue crack growth area and instantaneously fracture area.The second phase particles conduced to crack initiation.

2009 Vol. 29, No. 1