航空材料学报

2012, 32(5): .

[Abstract](1608) [PDF 278KB](252)

Abstract:

First Principle Calculation of Elastic Constant and Minimum Thermal Conductivity of La₂Zr₂O₇ Ceramic

XIANG Jian-ying, HUANG Ji-hua, CHEN Shu-hai, LIANG Wen-jian, ZHAO Xing-ke, ZHANG Hua

2012, 32(5): 1-6.

[Abstract](2151) [PDF 1209KB](314)

Abstract:
Elastic constant and thermodynamic properties of La2Zr2O7 ceramic which are used for thermal barrier coating have been calculated by using the first principle pseudopotential method. These results show that the lattice parameter of optimized crystal structure is 1.0934 nm, and the cell energy is the lowest when the x (positional parameter of O (48f)) is 0.329. The La2Zr2O7 ceramic have high structure stability from the results of elastic constant C11,C12,C44, bulk modulus and shear modulus. The Youngs modulus E is 201.50GPa, and the Poisson's ratio is 0.274, the isotropy coefficient is 0.733 which means that La2Zr2O7 ceramic with some brittleness. The Debye temperature is 619.4K and the specific heat is 274.3Jmol-1K-1. The minimum thermal conductivity of La2Zr2O7 ceramic is 1.31Wm-1K-1, while the experiment value measured by laser pulse method is 1.55 Wm-1K-1, its error is 15.48%.

Influence of Secondary Phases on Dynamic Recrystallization Mechanisms in Extruded Mg-Zn-Y Magnesium Alloy

HE Wei-wei, ZHANG Kun, HUANG Min, DAI Sheng-long

2012, 32(5): 7-17.

[Abstract](2611) [PDF 5808KB](328)

Abstract:
The combination of low density and moderate strength makes wrought magnesium alloys well suited for the application where weight is of critical importance. In recent years, magnesium alloys containing rare earth Y element have been developed and extensively investigated. Mg-Zn-Y alloys have high specific strength and good creep resistance due to the presence of quasicrystals. The aim of the present study is to investigate DRX behavior and mechanism in extruded Mg-Zn-Y magnesium alloys with different secondary phases (I-phase and W-phase) using Gleeble-3800 thermo mechanical simulator at the temperature range of 250~400℃ (in step of 50℃) and in the strain range of 0.001~10s-1. The microstructures of the alloy in the different stages of processing were examined by optical microscopy (OM) and transmission electronic microscopy (TEM). The conclusions have been drawn from investigation are: at high temperature of 400℃ and strain rate of 1s-1, when true strain was low (0.1 or 0.3), DRX mechanism of alloy with I-phase is normal as the ordinary DRX. When the true strain was high (0.5), the DRX mechanism of alloy with W-phase is CDRX. At temperature of 300℃ and strain rate of 1s-1, when the true strain was low, DRX mechanism of alloy with W-phase is CDRX, and when true strain was higher, and its DRX mechanism was the RDRX. Because of the DRX mechanisms of alloys with different secondary phases are different, the effect of temperature on microstructure of the alloy after deformation were also different. For alloy with I-phase, grain size of DRX was decreased with deformation temperature increased but for alloy with W-phase, DRX grain grows abnormally. The microstructure of alloy with W-phase after deformation could be refined efficiently by increasing the strain.

Analysis of Thermal Load of Dies for P/M Superalloy Isothermal Forming

ZHANG Ming-jie, LI Fu-guo, WANG Shu-yun

2012, 32(5): 18-25.

[Abstract](2012) [PDF 2936KB](303)

Abstract:
The finite element models of dies used for P/M superalloy disk forming were established, and the heating parameters were optimized based on the thermal-physical property of Ni-11Co-17W-6Al-8Ta alloy. The results show that stress peaks of the dies were lower when they were heated in heating rate range from 0.1℃/s to 0.5℃/s. The effect of holding time on thermal stress decreased when holding time was larger than 4h. This leaded to that the rate of decreasing stress became lower. According stress amplitude-holding time curve, the optimal holding time is between 2-4h. Moreover, at the heating rate of 0.1℃/s and the holding time of 2h, the outside surfaces and profile transition zones of dies exhibited stress concentration. The values of stress amplitudes were larger in these regions. However, the results of fatigue test at the temperatures of 1050℃ and 1100℃ show that the effect of thermal load on crack propagation in above-mentioned regions was slight.

Effect of PWHT on Microstructure and Mechanical Properties of Electron Beam Welded Joints of 300M Ultra-high Strength Steel

ZHANG Guo-dong, YANG Xin-qi, HE Xin-long, LI Jin-wei

2012, 32(5): 26-31.

[Abstract](2144) [PDF 3413KB](419)

Abstract:
The microstructure, tensile properties and Charpy V-notch impact toughness at room temperature of electron beam welded joints of 300M steel in the oil quenching+ tempering (WOQ), Normalizing 1+ oil quenching+ tempering (WN1OQ) and Normalizing 2+oil quenching+ tempering (WN2OQ) conditions have been investigated. And the mechanical properties of post weld heat treated joints were compared with base metal of oil quenching+ tempering (BOQ). Microstructure and impact fractography are investigated by SEM. Results indicate that these PWHT processes can't eliminate coarse columnar grains in weld metal, but the PWHT processes of WN1OQT and WN2OQ make the columnar grains morphology and the boundaries between weld metal and HAZ indistinctly. Mechanical properties of WN2OQ are significantly improved in comparison with WOQ. WN2OQ have higher ultimate tensile strength than BOQ, elongation and reduction of area reach 93.6% and 81% of the latter respectively and impact toughness is not less than BOQ. Impact fractography of WOQ is rough and columnar grains are pulled apart. Crack propagation is along with the columnar grain boundaries in some regions, this is the reason why oil quenched weld joints have a low impact toughness.

Precipitation Behavior of Silicide in Near-α TG6 Titanium Alloy

LI Juan, CAI Jian-ming, DUAN Rui

2012, 32(5): 32-36.

[Abstract](2035) [PDF 1205KB](289)

Abstract:
The precipitation behavior of silicide in near-alpha TG6 titanium alloy under the different heat treatment states was studied using OM, TEM. The results show that the silicide precipitates asymmetrically along the primary layer or in matrix. Silicide is HCP S2 type, generally long-rod or ellipsoidal precipitated inhomogeneously. There is no certain orientation relationship between the silicide and matrix. After a long period thermal exposure at 600℃, The size and amount of silicide increase with the extension of the heat exposure time. The interactions of silicide and dislocation cause the dislocation accumulation, which can effectively hinder dislocation glide to improve the alloy's strength.

Effect of Solution Treatment on Microstructures and Mechanical Properties of 7136 Aluminum Alloy

ZHU Ran-ran, ZHANG Yong-an, XIONG Bai-qing, LI Zhi-hui, LI Xi-wu, LIU Hong-wei, ZHU Bao-hong, WANG Feng

2012, 32(5): 37-42.

[Abstract](2223) [PDF 4074KB](294)

Abstract:
The effects of solution treatment on the microstructures and mechanical properties of 7l36 aluminum alloy extrusion plate were studied by OM,SEM,DSC and room temperature tensile test.The results show that the higher the solution temperature and longer time, the more coarse second phase dissolved. The overheated structure appears in the alloys when the quenching temperature is at 480℃. The trend of microstructure coarsening and recrystallization appears when prolongating the solution time is extended. The suited solution of the alloy is single-stage solution of 470℃,4 h. After solution and peak aging of (470℃,4 h)+(l20℃,24 h),the ultimate tensile strength,yield strength and elongation are 698 MPa,647 MPa and 12.8％,respectively.

Effect of Enhanced-Solid-Solution on Intergranular Corrosion and Exfoliation Corrosion Properties of 7085 Type Aluminum Alloy Containing Strontium

LUO Yong, XU Xiao-jing, ZHANG Yun-kang, SONG Tao, WANG Hong-yu, ZHANG Zhen-qiang, ZHANG Fu-bao, WU Gui-chao, WU Yao

2012, 32(5): 43-48.

[Abstract](2057) [PDF 2749KB](326)

Abstract:
The effect of enhanced-solid-solution treatment on the hardness, electrical conductivity, intergranular corrosion and exfoliation corrosion properties of strontium (Sr) microalloyed 7085 type aluminum alloy (Al-7.95Zn-1.80Mg-1.59Cu-0.15Zr-0.024Sr) was investigated by using microhardness testing, electrical conductivity testing, intergranular/exfoliation corrosion experiments, and optical and scanning electron microscopy observation. The results show that compared with the conventional solid-solution treatment (470 (C/2 h), the enhanced-solid-solution treatment (470 ℃/2 h+480 ℃/2h+490 ℃/2 h) advances the dissolution of coarse second phases. After being treated by the conventional T6 (121 ℃/2 h) ageing, relative to the conventional solid-solution treated alloy, the enhanced-solid-solution alloy exhibites a slightly lower hardness, slightly higher electrical conductivity, and a considerable improvement in intergranular corrosion and exfoliation corrosion resistances. The present experimental results demonstrate that the enhanced-solid-solution treatment is an effective tool to improve the anti-corrosion, especially the anti-exfoliation corrosion properties of Sr microalloyed 7085 type aluminum alloy.

Influence of Rare Earth Y on Structure and Properties of Mg-5Al-1.2Zn-0.8Sb Magnesium Alloy

ZHANG Jian-xin, GAO Ai-hua, GUO Xue-feng

2012, 32(5): 49-53.

[Abstract](1999) [PDF 1604KB](290)

Abstract:
The effects of rare earth Y on microstructure, mechanical properties and corrosion resistance of Mg-5Al-1.2Zn-0.8Sb alloy are studied when Y element is added into melt in the form of Mg-10Y interalloy with the range of 0~2.5% (mass fraction, similarly hereinafter). The experimental results indicate that Y element has the strong refinement on cast microstructure, the grain size maintains about 30 micron. When Y element changes from 0 to 2.5%, room temperature tensile strength of the alloy is increased in the range of 0 to 1.5% and decreased in the range of 1.5% to 2.5%, while its high temperature strength is improved in the range of 0 to 2.5% always. Y element can improve corrosion resistance of the alloy, when Y content is 1.0%, its corrosion resistance is more better, excessive Y added has negative effects on corrosion behavior of the specimen.

Microstructure Evolution of Spray Deposited SiC_P/Al-8.5Fe-1.3V-1.7Si during Exposure at Elevated Temperatures

HE Yi-qiang, TU Hong, FENG Li-chao, YANG Jian-ming, CHEN Zhen-hua

2012, 32(5): 54-59.

[Abstract](1979) [PDF 1363KB](285)

Abstract:
SiCP/Al-8.5Fe-1.3V-1.7Si composite prepared by spray deposition was densified by hot pressing, and then was rolled into the sheets. Evolution of second-phase dispersions, SiC/Al interface and dislocation density of the composite sheet during hot exposure were investigated, and phase transformation during hot exposure were analyzed by X-Ray Diffraction. The results showed that the dispersions kept fine without brittle phase formation and the SiC/Al interface kept clean. The second-phase grew hardly during the exposure at 500℃ for 200h. This phase grew slightly without obvious brittle phase formation during the exposure at 550℃ for 200h, while the phase coarsened rapidly when exposure temperature was above 550℃. Al4C3 phase formed near the SiC/Al interface, and dispersions grew to 400~500nm with Al13Fe4 phase formation after the exposing at 600℃ for 10 hours. Dislocation density increased along with the increase of exposure time at 550℃. Decomposition of SiC particles results in elevated Si concentration, and restrains Al12(Fe,V)3Si from coarsening and transforming into Al13Fe4. The composite is characterzied with good thermal stability when exposed below 550℃, heat resistance of the composite worsens when exposed above 550℃, dislocation is propogated during the exposure at 550℃.

Structure and Dry Tribology Performance of Plasma Sprayed Copper-Graphite Composite Coating

YUN Hai-tao, LIANG Bo, JI Heng, ZHENG Xue-bin

2012, 32(5): 60-65.

[Abstract](2120) [PDF 3314KB](289)

Abstract:
Graphite-65wt.%Cu composite coating was deposited by air plasma spraying on 316 stainless steel substrate using graphite-65wt.%Cu composite powder with the particles’ size in the range of 50~70μm. Microstructure and phase composition were characterized by field emission scanning electron microscopy (FESEM) with energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). Tribological properties of as-sprayed coatings were studied using the ball-on-disc friction and wear tester (UMT) under conventional conditions. The results show that the microstructure of as-sprayed coating is dense, which is well bonded with stainless steel substrate. The graphite particles uniformly distribute into the coating. The coating mainly consists of C, Cu and Cu2O phases. Graphite transfered film results in the low friction coefficient, and the experiment values are in the range of 0.03 to 0.15. Adhesion wear is the main wear mechanism.

Investigation of Flexural Strength of Vycor Glass/Silicone Composites Under High Temperature

HU Chun-ping, LIU Li, JIANG Bo, HUANG Yu-dong

2012, 32(5): 66-69.

[Abstract](2011) [PDF 1422KB](304)

Abstract:
The effect of temperature on flexural strength of vycor glass/silicone composites was studied.The results show that the flexural strength decreased with the increasing of the temperature.And there were three dramatical decrease zones existed between 200℃, 300℃ and 600℃. The structure of methyl-phenyl silicone resin at different temperatures was characterized by FT-IR spectrum.The thermostability of the matrix was investigated by using thermogravinetry.The thermodynamic parameters of composites at different temperatures were measured by dynamic mechanical analysis equipment.Meanwhile the morphologies of the flexural fracture surfaces of composites under different temperatures were characterized using SEM.All of the results show that the glass transition, the degradation and pyrolysis of the resin are the main reason that the flexural strength decreased.

Simulation and Investigation of Thermal Performance of Metallic Honeycomb Panel on Basis of ANSYS

FAN Zhuo-zhi, SUN Yong, PENG Ming-jun, WANG Kun

2012, 32(5): 70-74.

[Abstract](2060) [PDF 1032KB](336)

Abstract:
The heat transfer across metallic honeycomb panel was investigated by the simulation of finite element method on the basis of ANSYS. In consistent with the real experimental condition, the calculational model of metallic honeycomb panel was built. The steady thermal performance,mechanism of heat transfer and transient facial thermal response were investigated.In the condition of allowing for the coupling heat transfer, the research indicates that simulative results of the steady thermal performance are identical with the calculational results of the Swann Pittman empirical formula. Furthermore, the simulative results of transient facial thermal response are also quite indentical with the experimental results. All the results indicate that the finite element method of ANSYS could correctly simulate the heat transfer of the metallic honeycomb panel. In addition, the radiation heat transfer between the inner faces is one of the important mechanisms of heat transfer. Coupling heat transfer of the radiation and conductivity should be considered in the condition of high temperature.

Curing Conditions and Dielectric Properties of Chromium Based Wave-Transparent Material Matrix

YU Ji-qiang, LIU Jing-song, HUO Ji-chuan

2012, 32(5): 75-78.

[Abstract](1938) [PDF 2340KB](310)

Abstract:
Using zinc oxide as curing agent and silicon dioxide as filler, mixed with chrome-alumina phosphate, the matrix of chromium based wave-transparent materials were prepared. The curing temperature range of matrix was obtained by DSC-TG testing. Based on the DSC-TG analysis, the electrical properties under different temperature points were investigated companied with SEM, XRD and IR analyses. Finally, the best curing condition of the chromium based wave-transparent materials was obtained as that the temperature is 180℃ and the time is 2h.

Study on Novel Heat Resistant Cyanate Ester/phosphate Aluminum Composite

XUE Jie, GUAN Qing-bao, LIU Ping, LIANG Guo-zheng

2012, 32(5): 79-85.

[Abstract](1973) [PDF 2267KB](211)

Abstract:
Based on the outstanding integrate properties of both cyanate ester (CE) and phosphate aluminum (AlPO4), AlPO4/CE composites were designed and prepared in this work by employing the "composite technology". The effects of the coupling agent type and AlPO4 content on the properties of the new composites are discussed. Results show that different coupling agents have different effects on the interfacial adhesion between AlPO4 and CE. AlPO4(KH-550) and AlPO4(KH-560) have stronger interfacial effects than AlPO4(H-2), and AlPO4(KH-550)/CE has the optimum properties among the three composites. Moreover, AlPO4(KH-550)/CE composite with desirable AlPO4(KH-550) content has better properties than CE resin.

Tensile Strength of Composite Double-Lap Joint

LIU Sui, GUAN Zhi-dong, GUO Xia, LIU Jia, QIU Tai-wen, SUN Kai, CHEN Ping

2012, 32(5): 86-91.

[Abstract](2288) [PDF 2532KB](284)

Abstract:
An experimental and analytical study on ultimate tensile strength of composite double-lap joints with different adhesive thicknesses is employed in the paper,test results indicate the major failure mode of joints is adhesive shear failure and the ultimate strength of joints increasing with thicker adhesive. Analytical model is developed to investigate the adhesive failure of double-lap joint based on the experiments. The model takes into account anisotropy of each ply in the composite laminates and elastic-perfectly plastic behavior of the adhesive in the joints. The validity of analytical model for calculating shear strain/stress distribution is certified by comparing with finite model results. Maximum shear strain criterion is adopted in the analytical model to predict the ultimate tensile load of double-lap joint. Good agreement of the analytical predictions with the experimental results is obtained.

Strength Prediction for Al-Cu-Mg-Ag Alloy Based on Support Vector Regression

TANG Jiang-ling, CAI Cong-zhong, HUANG Si-jie, XIAO Ting-ting

2012, 32(5): 92-96.

[Abstract](1938) [PDF 802KB](213)

Abstract:
To explore the strength properties of Al-Cu-Mg-Ag alloy at different aging temperature and aging time, the support vector regression (SVR) approach combined with particle swarm optimization (PSO) algorithm was proposed to construct a SVR model based on experimental data. In the modeling process, the aging temperature and aging time were employed as input parameters, the tensile strength and yield strength acted as outputs. By comparison with BP neural network, it was found that the prediction accuracy of the established SVR model was higher than that of BPNN model by applying identical training and test samples. This investigation would provide a theoretical foundation for further study on the effect of aging condition on mechanical property, and the optimal design of the aging process for fabricating Al-Cu-Mg-Ag alloy.

Fatigue Crack Propagation and Delamination Behavior of Advanced Fiber Metal Hybrid Laminate

HUANG Xiao, LIU Jian-zhong

2012, 32(5): 97-102.

[Abstract](1900) [PDF 2137KB](244)

Abstract:
To study damage tolerance behavior of one kind of advanced hybrid laminate, this article accomplished fatigue crack propagation test under R=0.1 or -1 for two kinds of saw-cut length and two kinds of lay-up, compared and analyzed a-N data, obtained the delamination shape between each layers by etching the aluminium sheet. The result indicates that this advanced hybrid laminate obviously displays a better fatigue crack propagation property than aluminium sheet under R=0.1. The laminate with adhesive film around the prepreg performs a better fatigue crack propagation property than the laminate without adhesive film around the prepreg. The specimen with shorter saw-cut length shows a better fatigue crack propagation property than the specimen with longer saw-cut length for the bridging mechanism. Crack in central aluminium sheet is shorter than the others. The delamination shape between inner aluminium sheet and prepreg presents a triangle.

2012 Vol. 32, No. 5