航空材料学报

HRTEM Study of Strengthening Precipitates of Secondary Hardening Ultra-High Strength Steel

LI Jie, Li Chunzhi, GUO Feng, LI Zhi, YAN Minggao

2008, 28(4): 1-5.

[Abstract](1346) [PDF 1447KB](345)

Abstract:
The precipitates found in the ultra-high strength steel AerMet100 aged at 482℃ for 5h were investigated using High Resolution Transmission Electron Microscope(HRTEM).Fast Fourier Transformation(FFT) patterns obtained from lattice images were indexed to identify the nature of these particles.It is discovered in the results that the precipitates are mainly consisted of two types of particles,one is the well-known rod-like M2C carbide with 9.6nm in length and 3.1nm in diameter,and orientation relationship with martensitic matrix is(101)M∥(001)M2C,[010]M∥[100]M2C.The other is ellipsoidal Fe2Mo intermetallic compound(Laves phase),with 6.5nm in diameter,and orientation relationship is(211)M∥(001)L,[111]M∥[100]L.Both of them are dispersed in the matrix of fine lath martensite,and both of them,equivalent in size,are strengthening phases.

Effect of Trace Element Ag on Microstructure and Properties of Al-Cu-Mg-Mn-Zr Alloy

LU Congge, PAN Qinglin, HE Yunbin, LI Wenbin, LIANG Wenjie, LI Yunchun, ZHOU Yingchun

2008, 28(4): 6-11.

[Abstract](1151) [PDF 910KB](202)

Abstract:
The effects of trace element Ag on the microstructure and mechanical properties of an Al-5.3Cu-0.8Mg-0.3Mn-0.15Zr thin plate alloy were investigated by means of tensile testing,optical microscopy(O.M.),scanning electron microscopy(SEM) and transmission electron microscopy(TEM).The results show that the trace Ag addition can accelerate the hardening effect of the aged alloy and reduce the time to peak-aged.The mechanical properties can be improved at room and elevated temperatures,which is attributed to a much smaller dispersive Ω precipitation of thin plate shape.Meanwhile the ductility of the studied alloys remains at a higher level.The major strengthening phases of the alloy without Ag are θ′ precipitation and less S′ precipitation,while the strengthening phases of the alloy with Ag are Ω precipitation and less θ′ precipitation.After the solution and ageing treatment,the two alloys are both recrystallized totally.

Influence of Element W and Microstructure Evolution on Lattice Parameters and Misfits of Nickel-Base Superalloys

TIAN Sugui, XIA Dan, LI Tang, MENG Fanlai, WANG Minggang, YU Xingfu

2008, 28(4): 12-16.

[Abstract](1322) [PDF 2093KB](450)

Abstract:
By means of microstructure observation and XRD diffraction analysis,the influence of element W and microstructure evolution on the lattice parameter and misfit of the nickel based superalloys was investigated.Results show that,after full heat treatment,the γ′phase in the 7.5%W nickel based superalloy is coherently embedded and homogenously distributed in the γ matrix phase.The diffraction peaks of the γ′/γ phases in the nickel based superalloy move towards left side with the increase of the element W,which results in the increase of the lattice parameters of γ′/γ phases.The reasons of the parameter increase of γ′phase in the large extent is attributed to the more element W distributed in γ′phase,which causes the misfit of γ′/γ phases to transform into the positive value from the negative value.After full heat treatment,a lower misfit value of γ′/γ phases is displayed in the superalloy,and the parameter of γ phases increases in the large extent at the role of the applied stress during tensile creep,therefore increases the absolute value of the misfit of γ′/γ phases.

Effect of Inclusion Volume Fraction and Average Spacing on Fracture Toughness of High Co-Ni Ultra-High Strength Steel

GUO Feng, LI Jie, LI Zhi, WANG Junli, GU Lixin, WANG Rui

2008, 28(4): 17-21.

[Abstract](1310) [PDF 1118KB](188)

Abstract:
The fracture mode of high Co-Ni ultra-high strength steel belongs to the type of coalescence of voids.The fracture toughness of such steel was strongly affected by the following inclusion parameters: the nature of the inclusion,the size,the volume fraction,the average spacing among the inclusions,and the resistance to void nucleating.Suppose the microstructure and the resistance to the void nucleating were similar for different heats.The effects of the inclusion volume fraction f and the average spacing X0 on the critical crack tip opening displacement δIc of high Co-Ni ultra-high strength steel were estimated.The results showed that the relationship between the f-1/3,X0 and the δIc would be linear.In other words,such results dictated that as the volume fraction decreasing and the average spacing of the inclusion broadening,the fracture toughness of high Co-Ni ultra-high strength steel would be increasing.

Phase Characteristics of DD3 Single Crystal Superalloy

HAN Mei, LUO Yushi

2008, 28(4): 22-26.

[Abstract](1286) [PDF 312KB](305)

Abstract:
The characteristics of DD3 single crystal superalloy were investigated with physicochemical phase analysis method.Chemical compositions,mass fractions and approximate formulas of γ′phase and carbides in DD3 single crystal superalloy as cast and heat treatment condition were determined with Phase Extraction method.γ′sizes,chemical compositions of matrix and partition ratios of γ′/γ were analyzed and calculated from the result of electrochemical extracting of the precipitates.The comparison of phase characteristics of DD3 as cast and heat treatment show that heat treatment increases the mass fraction,decreases the size of γ,and changes the phase composition and partition behavior of elements.As a result,the strength and stabilization of γ′are improved with heat treatment.

Microstructure and Properties of Friction Stir-Processed AZ91 Magnesium Alloy

LüQinyun, SHA Guiying, WANG Hongshun

2008, 28(4): 27-30.

[Abstract](1229) [PDF 1089KB](255)

Abstract:
Friction stir processing was applied to AZ91 magnesium alloy with 3 different parameters:400rpm-100mm/min,800rpm-100mm/min,800rpm-200mm/min.The microstructure,tensile properties and micro-fracture mechanism of the alloy were analyzed before and after processing.The results suggest that the friction stir processing at the parameter of 800rpm-100mm/min can cause apparent grain refinement,significant improvement in ductility and ultimate strength,best comprehensive tensile strength of the AZ91 alloy.moreover,the fracture of the alloy takes on a feature of toughness fracture.The improvement in microstructure and properties was due to the dynamic recrystallization during FSP,which refined the grains of the alloy efficiently,and the dissolution and brokenness of the β phase during FSP.

Microstructures and Tensile Properties of LD2 Joint Brazed with a New Low-Melting Point Aluminum-Base Filler

MA Wenli, WU Sujun, MAO Wei, GUO Wanlin, CHENG Yaoyong

2008, 28(4): 31-35.

[Abstract](1234) [PDF 1480KB](150)

Abstract:
LD2 aluminum alloy was vacuum brazed at 530~550℃ using a new low-melting point(513~529℃) aluminum-base filler.The tensile strength of the joint were measured at room temperature and the fracture morphology and microstructure of the joint were examined using SEM and EDS.The results showed that sound joint could be obtained using the new low-melting point aluminum-based filler at optimum parameters with average room temperature tensile strength over 300MPa,and fracture morphology showed the characteristics of typical ductile fracture with dimples.

Superplastic Extrusion of Alumina-Based Fine-Grained Ceramic Composites for Turbine Disk

ZHANG Kaifeng, WANG Fei

2008, 28(4): 36-40.

[Abstract](1245) [PDF 497KB](192)

Abstract:
3Y-ZrO2/Al2O3 fine-grained ceramic composite compact was prepared at 1450℃ using vacuum hot-press sintering from high-purity Al2O3 powder and ZrO2(3Y-TZP) powder.Subsequent superplastic extrusion on turbine disk model was attempted at temperature range of 1500℃ to 1650℃.The results demonstrated that the material showed the best formability for extrusion at 1600℃,at which the maximum extrusion pressure was less than 25MPa and the maximum punch speed was up to 0.14mmmin-1.Deformed samples owned good quality and there were no apparent flaws.Comparing with undeformed sample,extruded samples were observed apparent coarsening in grain size,while its density was higher.SEM micrographs of fracture surfaces showed that the main fracture type was transcrystalline fracture.There was no great change between deformed and undeformed material about the mechanical properties such as flexural strength,fracture toughness and Vichers-hardness.Moreover,the disk exhibited higher mechanical properties and flexural strength,fracture toughness and Vichers-hardness increased from 573 MPa,7.1 MPam1/2 and 17.7 GPa to 617 MPa,8.1 MPam1/2 and 18.8 GPa respectively.

Glass-Forming Ability and Thermal Stability of (Gd-Tb)-Al-Co Glass Alloys

MA Lili, LI Ran, PANG Shujie, MA Chaoli, ZHANG Tao

2008, 28(4): 41-45.

[Abstract](1334) [PDF 2001KB](158)

Abstract:
Glass-forming ability(GFA) in(Gd-Tb)-Al-Co system were evaluated.The melting and solidification characteristics of corresponding alloys were determined by differential scanning calorimeter.The results of glass formation and thermal analysis reveals that the binary rare-earth based metallic glass alloys,(Gd-Tb)-Al-Co,have higher GFA than single rare earth based alloys,Gd-Al-Co or Tb-Al-Co.The(Gd0.5Tb0.5)55Al25Co20 alloy,which has the highest GFA with the critical diameter of 5mm by copper mold casting,is on the steep side of liquidus surface and near the eutectic point.Compared with Gd55Al25Co20 and Tb55Al25Co20,the coexistence of Gd and Tb decreases the solidification temperature of the corresponding alloys,consequently stabilize the liquidus structure and improve the GFA of the resulting alloys.

Study on Preparation and Structure of Giant Magnetoresistance La_1-xZn_xMnO₃ Compounds

LUO Guangsheng, LIU Guanghua, ZHOU Zhengyou, GAN Jianping, OUYANG Xiaolü

2008, 28(4): 46-50.

[Abstract](1112) [PDF 564KB](332)

Abstract:
The preparation and structure of perovskite manganese oxides were studied.When the temperature and sintering time in the solid reaction were above 1300℃ and 6h respectively,ZnO reacted with MnO2 into ZnMnO3 compound with a tetrahedron structure and the influence of molding pressure on structure was studied.The samples La1-xZnxMnO3 with different Zn2+ doping content(x=0.1,0.3,0.5,0.7,0.9) were prepared under the temperature 1350℃ and sintering time 12h,however,the other phase was formed when doping content was above 0.5 and affected giant magnetoresistance property.

Ion Assisted Deposition Al Film for Improving Fretting Fatigue Resistance of Ti811 Alloy at Elevated Temperature

ZHANG Xiaohua, LIU Daoxin, TAN Hongbin, WANG Xiaofeng, XI Yuntao, TANG Bin

2008, 28(4): 51-55.

[Abstract](1144) [PDF 1102KB](264)

Abstract:
To improve fretting fatigue resistance(FFR) of Ti811 titanium alloy at elevated temperature,Al film was produced on the Ti alloy surface by ion assisted multi-arc deposition(IAD) method.The composition distribution,bonding strength,micro-hardness,wear resistance of the IAD Al film were compared with multi-arc ion plating(MIP) Al film.The influence of the IAD Al film on FFR of the Ti alloy was evaluated.The results indicated that IAD technique could prepare Al film with low hardness,excellent bonding strength and good lubricating property.The IAD Al film significantly improved the fretting fatigue resistance of the Ti alloy at 350℃.

Study of Abradable Seal Coating with Nanostructure Y-PSZ Reference-Phase Used in High Temperature

GAO Zhongbao, CHENG Xudong, WANG Ming, ZHANG Zijun, DENG Feifei

2008, 28(4): 56-59.

[Abstract](1260) [PDF 765KB](275)

Abstract:
The preliminary performance of the abradable seal coating used in high temperature was researched.The tiny,soft and aggregated material powder compounded by Y-PSZ matrix,tender material and pore-forming component was prepared for the abradable seal coating.Then the coating was deposited triumphantly on the 1Cr18Ni9Ti alloy by means of APS,the thickness was more than 1.0mm.Microstructure,superficial Rockwell hardness and adhesive strength were analyzed and discussed.It was found that the superficial Rockwell hardness of the coating was in the distribution of HR45Y 30～55,the coating which was provided with 30% porosity had condign adhesive strength and hardness to satisfy the requirement.

Influence of Coating Temperature and Takeup Speed on Tensile Strength of SiC Fiber and Thickness and Surface Morphology of B₄C Coating

ZHENG Jie, LI Guojun, LI Baowei, HUANG Hao, LIU Xiaoguang

2008, 28(4): 60-64.

[Abstract](1307) [PDF 1378KB](184)

Abstract:
B4C coating on the W core SiC fibers were prepared via a CVD process.The influence of coating temperatures and takeup speeds on the tensile strength of SiC fibers,the thickness and the surface morphology of B4C coating were studied by scanning electronic microscope and tensile test.The results exhibited that it could not obtain B4C coating below a coating temperature of 1100℃.Above 1100℃ and under the given process parameters,the B4C coated fibers were obtained with a tensile strength close to the original fiber(~3339 MPa).To optimize the process parameters,it should satisfy that the coating temperature1210℃ and the takeup speed 0.055m/s,or the coating temperature 1210℃ and the takeup speed 0.055m/s.The coating temperatures affected the tensile strength of SiC fibers,the thickness and the surface morphology of B4C coating significantly.The takeup speeds affected the tensile strength of SiC fibers and the thickness of B4C coating.

Study on Adhesives in Bonding Fluorine Rubber to Metal

YAN Luke, KOU Kaichang, HA Enhua

2008, 28(4): 65-69.

[Abstract](1203) [PDF 1263KB](581)

Abstract:
Four kinds of adhesives(the modified Chemlok 607,OG,OG' and OGs adhesive) were developed for bonding fluorine rubber to metal,their properties were investigated in the same experimental conditions compared to Chemlok 607 and FA-1 adhesive.The results showed that the modified Chemlok 607,OG,OG' and OGs adhesive could be applied to bond fluorine rubber to metal directly,their properties in shear by tension loading were superior to Chemlok 607 and FA-1.The modified Chemlok 607 adhesive resolved the difficult problem for fluorine rubber to metal bonding could achieve good adhesion to metal.OG,OG' and OGs adhesive were ideal adhesives for bonding unvulcanized fluorine rubber to metal,could also be applied to bond silicone rubber,and used to bond fluorine rubber and metal in automobile synchrocyclotron.TGA(Thermal Gravimetric Analysis) showed that the cured OG,OG' and OGs adhesives had good heat-resistance and heat stability.The curing agent,4,4′-diaminodiphenylsulfone(DDS) could complex with fluorine rubber on interface in adhesives curing process,improved adhesion property with fluorine rubber.

Study on Microwave Absorbing Properties of Non-Woven Fabric Coating

ZHU Liqun, GU Jing, LI Weiping, LIU Huicong, ZHAO Bo

2008, 28(4): 70-75.

[Abstract](1179) [PDF 1582KB](223)

Abstract:
A fabric coating absorbing material(FCAM) with multi-layer structure was prepared on non-woven fabrics.In order to investigate absorption ability,composition(carbonyl iron power and acetylene carbon black at various ratios as absorbing agents) and structure(different multi-layer structures,including superposed directly and inserted fabrics which didn't have absorbing properties) of this absorbing material were respectively studied with 3cm wave-guide method at 9.35GHz.Results show that this multi-layer structure together with absorbing agents has an impact on transmitting route of microwave.Moreover,the electromagnetic waves may occur repeatedly energy dissipation through a series of dispersion,reflection in the multi-layers.As a result,resonance loss may be occurred.Because fabrics used were very light,this FCAM had a lower planar density.

Ti_xO_y-TiC_x-Ti₅Si₃/Glass-Ceramics Oxidation Protection Coating for C_f/SiC Composites

ZHENG Xiaohui, DU Yongguo, XIAO Jiayu, ZHANG Weijun, ZHOU Wenyuan, LU Yufeng

2008, 28(4): 76-81.

[Abstract](1243) [PDF 1388KB](197)

Abstract:
A novel multi-layer coating was designed and fabricated to hence the anti-oxidation property of carbon fiber reinforced silicon carbide(Cf/SiC).Titanium metalized coating was obtained using molten salt method,and MgO-Al2O3-SiO2(MAS)glass-ceramics were fired on metalized coating.The phase composition,and morphology of the multi-layer coating were characterized by X-ray diffraction,optical microscope,and scanning electron microscopy and energy dispersive spectroscopy.With the function of transition,sealing,anti-diffusion of carbon,self-sealing,anti-diffusion of oxygen and anti-vaporized,the coating was dense and the main composite was Tix-Oy-TiCx-Ti5Si3 /glass-ceramics.The coated Cf/SiC was submitted to thermal cycling tests up to 1000℃ in air.Weight loss was 0.0039g/cm2 and flexural strength restrained 99.3% after 12h of thermal cycling.

Microwave Absorbing Prediction of Fe₃O₄/Conductive Polyaniline Nanocomposites with Core-Shell Structure

HAN Xiao, WANG Yuansheng

2008, 28(4): 82-87,106.

[Abstract](1231) [PDF 797KB](304)

Abstract:
In consideration of the interactions of Fe3O4/ conductive polyaniline nanocomposites with core-shell structure,the effective electromagnetic parameter formula of the composite system was derived from the classical Maxwell-Garnett formula.The numerical simulation results show that the permeability of the surrounding media(μh) increases with the increasing volume fraction.The super-exchange electromagnetic coupling resonance phenomena of the electromagnetic parameter has made the microwave absorbing structure with the thickness of 2mm reach the maximum microwave attenuation when the proportion of core/shell is 0.6,and with the increasing volume fraction,the maximum microwave absorption peak increases and shifts to low frequency.The optimization results show that the four-level microwave absorbing structure with volume fraction of 0.3 has the optimal absorbing property and the minimum of reflectivity is-62dB.

Process Study on SiC Fillers into 3-D Carbon Fiber Perform by Slurry Infiltration

XIE Chongbo, XU Yongdong, WANG Yi, ZHANG Litong, CHENG Laifei, WANG Yiguang, TONG Changqing

2008, 28(4): 88-93.

[Abstract](1236) [PDF 1513KB](250)

Abstract:
In order to introduce a mass of SiC fillers into 10mm thick 3-D carbon fiber perform,four slurry infiltration method were applied: vacuum infiltration,pressure infiltration,pressure filtration,and vacuum suction straining.The volume fraction of introduced SiC fillers in carbon fiber perform and its distribution were investigated.The results showed that pressure filtration led to the best results.Using a slurry containing 4vol% 1μm SiC fillers,thrice infiltration introduced 27.4vol% SiC fillers,which packed densely and uniformly.

Prediction and Analysis of Equivalent Out-of-Plane Modulus of Honeycomb Core Materials

ZHAO Jian, XIE Zonghong, AN Xuefeng, ZHANG Ming, LIU Gang, MA Hongyi

2008, 28(4): 94-100.

[Abstract](1251) [PDF 667KB](502)

Abstract:
A simplified representative unit cell compared to Kelsey model's was selected,and the same analytical expressions exactly with Kelsey's model were obtained based on the theorems of minimum potential energy and minimum complementary energy.Finite element analysis were conducted on the representative unit,and the equivalent out-of-plane moduli of a group of commercial hexagonal honeycomb cores with different geometries were acquired.At last,numerical results from analytical model and FEA model were compared to the experimental data published by Hexcel Corporation.A set of modified formulas based on analytical model were derived to predict and analyze the equivalent out-of-plane moduli of typical hexagonal honeycomb cores.

Through-Thickness Compression Properties of Z-Pin Reinforced Foam Core Sandwich

DU Long, JIAO Guiqiong, HUANG Tao

2008, 28(4): 101-106.

[Abstract](1159) [PDF 1513KB](281)

Abstract:
As a novel sandwich structures,Z-pin reinforced foam core sandwich can overcome the limitations of traditional honeycomb core sandwich.A series experiments were carried out to investigate the responses of Z-pinned foam core sandwich under compressive loading,including inclination angles of 15 and 25 with foam core thickness of 12.7mm and 8mm,and each group of them had a contrasted one.Experimental results showed Z-pinned foam core could reinforce the compression modulus and strength of sandwich markedly,and had a deformation and failure map which was different from unreinforced one under compression.The thickness of foam core and inclination angle of pin were dominated factors of compression strength,by influencing the effective length of Z-pin buckling.Considered the actual restriction of face sheets,the existing compression strength model was ameliorated by employing restriction correction coefficient,made the prediction results approach and agree better with the measured results.

2008 Vol. 28, No. 4