航空材料学报

Study of Nb₃ Al Intermetallics Prepared by Laser Deposition

HE Jin-jiang, ZHONG Min-lin, LIU Wen-jin, ZHANG Hong-jun

2006, 26(5): 1-5.

[Abstract](1470) [PDF 973KB](345)

Abstract:
The Nb3Al intermetallics has been prepared from Nb-12Ti-22Al(at%)and Nb-22Al(at%)elemental powder blends by laser deposition on the substrate of Ti-6Al-4V.The laser power is important for successful synthesis.The average compositions of the deposited intermetallics are identical to the compositions of the elemental powder blend.The microstructure consists of δ-Nb3Al matrix and fine β-Nbss phase.It is found that there is a critical thickness for laser deposited layers free of cracks.With increase of deposited thickness,the prepared sample is inclined to fracture at the bottom,and the Nb-22Al is easier to crack without the addition of Ti.

Superplasticity of One Kind of Low Temperature Superplastic Titanium Alloy

ZENG Li-ying, ZHAO Yong-qing, LI Dan-ke, Li Qian

2006, 26(5): 6-9.

[Abstract](1381) [PDF 406KB](515)

Abstract:
Microstructures and superplastic properties of one kind of α plus β typed titanium alloy were studied in this paper.The results indicated that the maximum tensile elongations are all over 1600% for the alloy deformed from 740℃ to 800℃ with the primary strain rate of 1.11×10-3s-1;and which is 2149% for the alloy deformed at 760℃.The elongation is up to 1380% for the alloy deformed at 760℃ with the primary strain rate of 1.11×10-2s-1,which means,the alloy annealed at 700℃ for 1h possess superior low temperature high strain rate superplastic property during the mentioned testing temperature range.The grain size is as small as 0.89μm before superplastic deformation;and which is 1.51μm and 2.33μm,respectively for the alloy deformed at 740℃ and 760℃ with the strain rate of 2.22×10-3s-1.The principal superplastic deformation mechanism for the alloy is boundary sliding,assistant ones are deformations inside the grains and dislocations creep.

Effect of Al content on Microstructure and Property of a Cast Ni₃ Al-base Alloy with High W and Mo content

LI Qing, SONG Jin-xia, XIAO Cheng-bo, WANG Ding-gang, HAN Ya-fang

2006, 26(5): 10-13.

[Abstract](1064) [PDF 1041KB](259)

Abstract:
Based on a cast Ni3Al base superalloy IC6,a new conventional cast Ni3Al base alloy containing high amount of refractory elements,Mo,W,for strengthening has been developed as high temperature die material.Various contents of aluminum were added into the alloy to improve the oxidation resistance,and its effects on microstructure and mechanical property have also been studied.Microstructure of the alloy and morphology of oxide layers were analyzed by the scanning electron microscope(SEM)with the energy dispersive spectrometry(EDS)and phases of oxide layers were identified by the X-ray diffraction analysis(XRD).The results showed that with increment of aluminum content from 7wt% to 8wt%,the rate of mass gain became slower and spallation of oxides decreased,therefore the oxidation resistance of the alloy is improved.The results also showed that the alloy with 7.5wt%Al has the best comprehensive properties,while when the content of aluminum reached to 8wt%,high temperature mechanical strength decreased obviously due to excessive amount of primary γ'phases.

Effect of Melt Temperature and Cooling Rate on Microstructure and Mechanical Properties of Al-Fe-V-Si Heat-Resistant Aluminum Alloy

TAN Dun-qiang, LI Wen-xian, CHEN Wei

2006, 26(5): 14-17.

[Abstract](1420) [PDF 382KB](353)

Abstract:
The microstructure of Al-Fe-V-Si alloy prepared at different melt temperature and cooling rate are examined by methods of OM and XRD,and the mechanical properties of samples prepared by method of powder metallurgy are examined.Results showed that,the melt temperature and cooling rate have apparent effect on the microstructure and mechanical properties of Al-8.5Fe-1.3V-1.7Si alloy.At the same cooling rate,the higher the melt temperature,the finer are the microstructure of samples.And there is a suitable melt temperature to yield the maximal mechanical properties of samples.The primary phases compositions of samples mostly depend on the cooling rate,and the melt technology is suggested according to properties of Al-Fe-V-Si alloy.

Effects of Different Heat Treatment Temperature on Stress Rupture Properties of DD3 Alloy after Blowing Sand

YUAN Hai-long, LIU Shi-zhong, HAN Mei, LUO Yu-shi

2006, 26(5): 18-21.

[Abstract](1172) [PDF 1413KB](338)

Abstract:
Blowing sand was performed on DD3 alloy samples after standard heat treatment.Subsequently,the heat treatment of samples was carried out at different temperatures.The effects of the heat treatment temperatures on the stress rupture properties at 1000℃/195 MPa after blowing sand for the first generation single crystal superalloy DD3 were investigated.The results show that no recrystallization occurs at 1050℃ but coarse γ' phases precipitate and stress rupture property decreases.Recrystallization occurs at 1150℃ and the stress rupture property decrease notably.At 1250℃ treatment condition,recrystallization happens yet stress rupture property exhibit a high level because of finer γ' phases and good microstructures.

Influence of Microstructures on Mechanical Properties for TC21 Titanium Alloy

MA Shao-jun, WU Xue-ren, LIU Jian-zhong, WANG Li-fa

2006, 26(5): 22-25.

[Abstract](1242) [PDF 1037KB](426)

Abstract:
Mechanical properties,including tensile property,fracture toughness and fatigue crack growth rates,have been investigated for two different microstructures of two-phase titanium alloys,TC21.It was found from tensile test results that the lamellar microstructure has almost the same tensile strength but inferior ductility property compared with the basketweave microstructure.Fracture toughness of these two microstructures was improved by different mechanisms.Large crack growth rates of basketweave microstructure were found nearly the same with lamellar microstructure at lowerΔK range,but slower at higher ΔK range.The load direction on specimens has little influence on crack propagation behavior for these two types of microstructures.Transitions occurred in the Paris regime of crack growth rate curve of TC21,which are smilar to some other titanium alloys.

Effect of Homogenizing Annealing on AS-Cast Aluminum Bronze

XU Jian-lin, LU Yang, LIU Ming-lang, LI Hai-lan, LI Wen-sheng, WANG Zhi-ping, ZHU Xiao-wu

2006, 26(5): 26-30.

[Abstract](1239) [PDF 1244KB](376)

Abstract:
Microstructure and mechanical properties of a new high strength and wear-resistant as-cast aluminum bronze with different homogenizing annealing are investigated by means of SEM,XRD and X-ray spectrometer.The results show that the as-cast aluminum bronze can be eliminated casting segregation and improved mechanical properties.In homogenizing annealing,segregation atom can dissolve into matrix structure or form strengthening phase.Therefore,segregation microstructure is improved.If sphericity strengthening phase distributes equally on β matrix structure,the experiment alloy has good mechanical properties.Microstructure and mechanical properties of the experiment alloy primarily depend on homogenizing annealing temperature and time.According to contrast experiment,the best homogenizing annealing process is 950℃ and 9 hours.

Effects of Rolling Process on Microstructure and Properties of Ti600 Alloy Plates

HONG Quan, QI Yun-lian, LIU Xiang, ZHAO Yong-qing

2006, 26(5): 31-34.

[Abstract](1399) [PDF 447KB](218)

Abstract:
Ti600 alloy plate was chosen to study the influence of different rolling process and subsequent heat treatments on the tensile properties and creep resistance.Microstructure and mechanical properties have been investigated in common process and thermomechanical process(TMP).Effects of welding process on properties of Ti600 alloy plate were also studied.The results show that the thermomechanical process treated condition have superior creep resistance compared to common rolled process treated condition have superior creep resistance compared to common rolled process condition.Ti-600 alloy also possesses excellent properties after EB-welding process.

Effect of EBW Line Energy on Microstructure and Mechanical Properties of Ti-24Al-15Nb-1Mo Joint

YUAN Hong, GU Wei-hua, YU Huai, GUO Shao-qing, LI Xiao-hong, GU Jia-lin

2006, 26(5): 35-40.

[Abstract](1345) [PDF 745KB](283)

Abstract:
The effect of electron beam welding(EBW)heat input factors on Ti-24Al-15Nb-1Mo(at%)joint microstructure and mechanical properties was investigated.The suitable EBW parameter windows are then determined to attain satisfactory joint ductility and impact toughness.It is shown that the as-welded joint microstructure was composed of a small amount of retained β/B2 phases and β-transformed microstructures including secondary α2,some Ο phase and ω phase.It is indicated that the coarsening grain size,the existence of retainedβstructure,reducing B2 phase and disappearance prime α2 phase and Ο phase,as well as formation of ω phase together with the growingα2/O colony as the heat input increased in welding are the main reasons for the decrease of the strength and the ductility of the joints.

Wettability of Pd-Ni Based Brazing Fillers on Si₃N₄ Ceramic and Interfacial Bonding

CHEN Bo, XIONG Hua-ping, MAO Wei, CHENG Yao-yong, YE Lei, WU Xin, LI Xiao-hong

2006, 26(5): 41-45.

[Abstract](1567) [PDF 713KB](282)

Abstract:
The wetting behavior of PdNi, PdNi-(5-14)Cr and PdNi-(15-26)Cr on Si3N4 was studied by the sessile drop method.The results show that on the heating condition at 1250℃ for 30 min in vacuum,the filler metal's wettability of the filler metal on Si3N4 is improved by increasing the Cr content.For Pd60-Ni40 brazing filler,mainly Pd-Si and Ni-Si phases were formed as the reaction products with Si3N4.When active element Cr was added into Pd-Ni filler,Cr also participated in the interfacial reaction,that is,for PdNi-(5-14)Cr brazing filler,a black and thin Cr-N layer was visible in the reaction layer.In the case of PdNi-(15-26)Cr filler,the Cr-N layer was formed just at the interface close to the Si3N4.

Microwave Absorbing Properties of Activated Carbon-Fiber Felt Dipole Array/Epoxy Resin Composites

ZOU Tian-chun, SHI Chun-sheng, ZHAO Nai-qin

2006, 26(5): 46-50.

[Abstract](1425) [PDF 987KB](280)

Abstract:
Microwave absorbing properties of the composites containing activated carbon-fiber felt dipole arrays(ACFFDAs)were investigated.The results show that the absorbing performances of the composites containing ACFFDAs are affected greatly by the direction of the incident electric field,the resistance connecting the two arms,the space between dipoles and the position of the array in the sample.The microwave absorption of the composites containing ACFFDAs presents anisotropy.When the dipoles are parallel with the incident electric field,the composites show better absorbing effect.The absorbing properties rise at first and then fall with increasing the resistance connecting arms or the space between dipoles, that is,the resistance and the space have the optimum values respectively.The absorption effect is improved with decreasing the space between the dipole array and the bottom surface of the sample.In this work,when the dipoles are parallel with the incident electric field,the composite obtains a reflection loss below-10dB over 13GHz and the minimum value reaches-30.3dB.

Study of Relationship between Structures and Mechanical Properties of Three-Dimensional Angle-Interlock Woven Carbon/Resin Composites

YANG Cai-yun, LI Jia-lu, CHEN li, ZHANG Guo-li

2006, 26(5): 51-55.

[Abstract](1398) [PDF 1048KB](437)

Abstract:
The paper investigated the mechanical properties of three-dimensional angle-interlock woven carbon/resin composites,which have four different kinds of weave structures.3D woven composites with different structures were designed and produced,and their mechanical properties were assessed using tension,bend and compression tests.Results show that the differences of tension,bend and compression properties are great,around 2 times;stuffer warp and stuffer weft improve mechanical properties notably;interphase breakage between fiber and resin is the first failure mode of 3D woven composites;No.1 composites with stuffer warp and stuffer weft has the best mechanical properties among the four different kinds of structures composite.Finally it is predicted that improving interphase binding energy must increases mechanical properties.

Correlation between Pre-Oxidation Processing and Oxygen Content of PAN-Based Oxidized Fibers

JING Min, WANG Cheng-guo, ZHU Bo, WANG Yan-xiang, DING Hai-yan

2006, 26(5): 56-60.

[Abstract](1110) [PDF 226KB](393)

Abstract:
The content of oxygen element in preoxidized fibre(OF)can be regarded as the characterization of pre-oxidation extent.The differential thermal analysis,thermalgravimetric analysis and elemental analysis are used to determine the content of oxygen element in preoxidized fibre,analyze how the water asorptivity effects the determination of the oxygen element content,discuss the relationship between temperature,running speed,drawing and the oxygen element content.The results show that the effect of water asorptivity on the determination of the oxygen element content in PAN precursor is stronger than that in preoxidized fibre;The oxygen element content increases when temperature increases and more temperature,more increment;The oxygen element content is higher when the running speed is slower at the same temperature; The drawing is good for the oxygen diffuseness in OFs;Those OFs which oxygen content lies near or between 10-12% may produce good CFs otherwise it can't do.

Effect of Pyrolysis Temperature on Structure and Properties of 2D-C_f/SiC Composites Fabricated by Precursor Pyrolysis

JIAN Ke, CHEN Zhao-hui, MA Qing-song, ZHENG Wen-wei, HU Hai-feng

2006, 26(5): 61-64.

[Abstract](1431) [PDF 651KB](246)

Abstract:
Two-dimensional carbon fiber cloth reinforced silicon carbide(2D-Cf/SiC)composites were fabricated with polycarbosilane(PCS)and divinylbenzene(DVB)as precursors and SiC as inert fillers.The effects of the pyrolysis temperature in the first cycle on the microstructure and mechanical properties of Cf/SiC composites were investigated.The results showed that increasing the first pyrolysis temperature could decrease the interfacial bonding force between carbon fiber and SiC matrix.As a result,the composites fabricated with higher pyrolysis temperature exhabit better mechanical properties.When the pyrolysis temperature of the first cycle raised from 1000℃ to 1600℃,the flexural strength,shear strength and fracture toughness enhanced from 200.7MPa,16.8MPa and 7.4 MPa·m1/2 to 200.7MPa,16.8MPa and 7.4 MPa·m1/2,respectively.

Study on Processability Properties of Resin/Carbon Cloth Composite Curing at Moderate Temperature

Wu Yun-qiqige, LIAO Zi-long

2006, 26(5): 65-69.

[Abstract](1221) [PDF 895KB](339)

Abstract:
It has been reported in this paper that the curing process parameters of the resin were determined by the methods of the curves of viscosity-temperature and gel time-temperature as well DSC of the resin.The mechanical properties of the composites made of the prepregs impregnated in both solvent and hot-melt methods were compared.The results showed that the "hot-wet" environments-resistance of the letter was better than the former.The analysis of the SEM on the fracture surfaces of composite showed that bonding between the fiber and resin of composite was good.

Preparation of Thermoplastic Elastmer Protect Coating for Chemical Milling of Aluminum Alloy

WANG Yun-ying, MENG Jiang-yan, LIN Cui

2006, 26(5): 70-72.

[Abstract](1587) [PDF 214KB](299)

Abstract:
This study adopted thermoplastic elastmer as the base material of protect coating for chemical milling of aluminum alloy.The experiment included synthesis of PF resin;preparation of protective coating with different kinds of formula;analysis of the performances of protective coating: such as appearance,viscosity,solid content,tensility,rupture elongation ratio,etching ratio,compatibility,peel ability and so on.Finally,the performance of the protect coating is compared with that of the similar products of the USA.Experiment proves that characteristics of the self-produced protective coating,such as transparent uniform film,proper peel strength,perfect aldaline resistance,meets the requirements of chemical milling,approaches that of American products basically.

Influence of Surfactants on Impregnation Performance of Coal Tar Pitch

SONG Fa-ju, LI Tie-hu, WANG Da-wei, ZHOU Zhen-zhong

2006, 26(5): 73-76.

[Abstract](1298) [PDF 430KB](262)

Abstract:
The effects of the surfactants on the impregnation performance of coal tar pitch are studied in this paper.The results show that the softening point and viscosity of the pitch are significantly decreased by modified with surfactants.These characters are helpful for the impregnation,although the carbon yield decreases slightly.The modifying mechanisms of surfactants on coal tar pitch are also discussed.

Investigation on Influence of pH Value on Phase and Microstructure of Yttrium Silicates Coatings

HUANG Jian-feng, DENG Fei, WU Jian-peng, LUO Hong-jie, CAO Li-yun

2006, 26(5): 77-80.

[Abstract](1454) [PDF 349KB](212)

Abstract:
Yttrium silicates coatings were prepared with a novel hydrothermal electrodepostion method on the graphite surface directly.The phases and microstructures of the coatings were characterized by XRD,EDS and SEM analyses.The influence of pH value of the precursor solution on the phase and microstructure was investigated primarily.It showed that the yttrium silicates coatings could be obtained with the pH value in the scope of 1.5~3.0 at 150℃.With the increase of pH value,micro-cracks and micro-pores of the coatings decrease;and the crystallinity and density of the coatings have been improved correspondingly.

Optimum Design and Simulation Analysis of Temperature Field on Sapphire Crystal Growth with GOI Method

XU Cheng-hai, MENG Song-he, DU Shan-yi, ZUO Hong-bo, ZHANG Ming-fu

2006, 26(5): 81-85.

[Abstract](1457) [PDF 897KB](389)

Abstract:
With the help of numerical simulation on temperature field,we get the result that additional axial and radial temperature gradient can increase the stability of interface,decrease thermal convection of fused mass and improve the quality of crystal growth.According to the temperature field requirement for growing large size sapphire,the conventional GOI furnace was modified with designing special shape of heater and structure of heat shield.It can provide controllable axial and radial temperature gradient for the system of crystal growth.It is indicated that the improved temperature field furnace could grow better quality large size sapphire.

FEM Simulation and Optimization Design of Flow Field in CVI Reactor

CHEN Jin, XU Yong-dong, ZENG Qing-feng, ZHANG Li-tong, CHENG Lai-fei

2006, 26(5): 86-90.

[Abstract](1209) [PDF 1059KB](194)

Abstract:
Chemical vapor infiltration(CVI)is an essential process to manufacture the Continuous Fiber Reinforced Ceramic Matrix Composites.In order to optimize the manufacturing process,a systemic and in-depth study on simulating the flow field of CVI reactor is very important.The flow fields of CVI reactors were simulated by finite element method(FEM)based ANSYS-FLOTRAN of commercial software.For the simple shape component,the flow field is influenced evidently by the lay-mode and arrays of components.The boundary conditions of components are more uniformity and symmetry by parallel arrays of components than that of cross arrays,so the circumfluence in the CVI reactor was decreased.The velocity and pressure difference of the mixed gas were increased with the increase and uniformity of components in parallel arrays.It is key to improve the chemical vapor infiltration quality that reducing the free-space in the CVI reactor.Under the principle of reducing free spacing in CVI reactor,the flow field could be improved by the guide plates in CVI reactor with complex non-conventional shape components,and the circumfluence could be avoided around the components,so the flow fields were optimized.

Numerical Simulation of High Temperature Thermal Chemical Ablation for Carbon Composite Material

LIU Zhi-gang, LIANG Jun, ZHANG Wei

2006, 26(5): 91-95.

[Abstract](1388) [PDF 262KB](215)

Abstract:
The calculation method of thermal chemical ablation was discussed in the paper.Numerical simulation of high temperature thermal chemical ablation for carbon composite material was done and the ablation results were calculated.The processes of oxidation and sublimation were appered in the ablation for carbon composite material.The alternant temperature of oxidation and sublimation was 3300K under 10atm.The alternant temperature would raised when pressure raised.The result of oxidation was CO.The result of sublimation was C3 and C1 gradually.The main reaction was 2C+O2→2CO under 3300K.The main reactions were 3C+O2→2CO,2C+N2→2CN and i(C)→Ci(g)i=1、3 above 3300K.The results were consistent with that of spectrum dignoses,which confirm the valid of thermal chemical calculation by minimum free energy method further.

Fatigue Behavior of LY12 Aluminum Alloy under Combined Tension and Torsion Loading

LIU Shi-min, AI Su-hua, WANG Zhong-guang

2006, 26(5): 96-100.

[Abstract](1401) [PDF 1014KB](269)

Abstract:
Fatigue properties of LY12 aluminum alloy samples under combined tension and torsion were investigated,and the fracture surfaces were observed through scanning electron microscopy.Axial tensioncompression,0° in-phase combined tension and torsion,45° out-of-phase combined tension and torsion,90° out-of-phase combined tension and torsion and fully reversed torsion loading paths were selected,and the same maximum effective strain was kept for the five loading paths.Cyclic hardening and saturation were observed under five loading paths.The fatigue life is the longest under fully reversed torsion and the shortest under 90° out-of-phase combined tension and torsion.The difference in fatigue life under five loading paths can be explained through Wang-Brown damage parameter.Fatigue striations can be seen on the fracture surfaces of samples under axial tension-compression and 0° in-phase combined tension and torsion,and extensive rubbing is apparent on the fracture surface of samples under 90° out-of-phase combined tension and torsion and fully reversed torsion.

Thermal Fatigue and Damage Behaviors of γ-TiAl

LI Jun, QIAO Sheng-ru, LI Shi-qiong, ZHANG Bin

2006, 26(5): 101-105.

[Abstract](1473) [PDF 365KB](173)

Abstract:
The thermal fatigue tests of γ-TiAl were carried out,in air,on the thermo-mechanical fatigue apparatus which heated by ray radiation.The damage of specimen owing to thermal fatigue was evaluated by the relative varieties both of Young`s modulus and electrical resistance,and the phase transformation and microstructure was analyzed also.The results indicated that the change tendency of damage curve which characterized by relative variety of the electrical resistance consisted with that of Young`s modulus.The damage curves evaluated by two kinds of method both had the two stages,that were liner and stable damage.At liner damage stage,the difference between the two curves was small,whereas the difference was remarkable with the increase of number of cycles,and finally,both tended to a stable constant.After thermal fatigue,the content of γ phase increased,and α2 decreased accordingly.The increment of γ phase thermal fatigue in 200~900℃ was more than that in 200~700℃.After thermal fatigue,the size of lamellar reduced,and flaws,such as micro-holes,were appeared.These varies lead to the increase of electrical resistance and the decrease of Young`s modulus.

Investigation of Tensile Fracture Behavior of Directional PMMA

FAN Jin-juan, ZHANG Wei-fang, CHEN Xin-wen

2006, 26(5): 106-108.

[Abstract](1505) [PDF 903KB](444)

Abstract:
Tensile fracture behavior of directional PMMA at different temperature is investigated.And the relationship between tensile behavior and temperature is discussed.The result shows with the temperature increasing,tensile strength and modulus decreases but elongation increase and material properties change from rigidity to flexibility.Fracture characteristics of directional PMMA are obviously different at different temperature.Fracture faces exhibit delamination features at 23℃,fireworks features at -55℃ and flexibility features at 80℃.

Study on Fatigue Crack Propagation Behavior of YB-MD-3 PMMA Plates

JIA Jing-hua, LI Ya-zhi, XIAO Jian

2006, 26(5): 109-112.

[Abstract](1154) [PDF 747KB](924)

Abstract:
An experimental study of stable fatigue crack propagation behavior and the measurement of fatigue crack propagation thresholds of YB-MD-3 PMMA plates was carried out at room temperature.During the preparation of initial through fatigue cracks for M(T)specimens,load cycles with compressive portion demonstrates better quality than usual tension-tension loading.The fatigue crack propagation rate in Paris's region for certain load ratio shows good correlation with a straight line in double logarithmic da/dV-ΔK coordinate.The da/dN and the slope of the straight line increases with the increase of load ratio.For the negative load ratios,however,the compressive portion in load cycles accelerates the crack growth.A proper formulation to these effects is unavailable.The fatigue crack propagation rate in YB-MD-3 plates is also sensitive to the change of load frequency at room temperature,even for very low frequencies,say,1Hz and 2Hz.

Reliability Analysis for Fiber Winding Chamber of Solid Rocket Motor via Stochastic Finite Element Method

CHEN Shun-Xiang, SHEN Zhi-hui, ZHU Cheng-yong

2006, 26(5): 113-116.

[Abstract](1158) [PDF 192KB](180)

Abstract:
Adopt extended Neumann stochastic finite element method(SFEM)to analyze the stress response of the fiber winding chamber of solid rocket motor(SRM)under the action of gas pressure with normal distribution,then analyze and compute the its reliability according to the stress strength interference principle.

2006 Vol. 26, No. 5