航空材料学报

Investigation on Behavior of Solid Copper-Induced Embrittlement of Titanium Alloy

LIU Dao-xin, LIU Shuang-mei, FAN Guo-fu

2006, 26(1): 1-5.

[Abstract](1518) [PDF 555KB](284)

Abstract:
The behavior of solid copper-induced embrittlement(SCIE) of TC11 titanium alloy was investigated using slow strain rate tests(SSRT) and constant load tensile tests(DLTT) at different temperatures.TC11 specimens were contacted with copper by using ion beam enhanced deposition and mechanical pressure methods.The results show that the SCIE susceptibility of TC11 alloy is high at 500℃,but it is not noticeable at 300℃ or 400℃ when SSRT methods are used.While employing constant load tensile tests,the mechanical properties of TC11 alloy are slightly influenced by contacted copper at 500℃,but the fracture life and ductility of the titanium alloy are decreased remarkably at 550℃ by copper pollution.The prerequisites for SCIE occurrence of this titanium alloy are as follow: copper must be in intimately contact with titaninm alloy surface,suitable temperature and strain rate are need.

Effect of Yttrium on the Microstructure of Ti-23Al-25Nb Alloy

SI Yu-feng, CHEN Yu-yong, KONG Fan-tao, CHEN Zi-yong

2006, 26(1): 6-10.

[Abstract](1481) [PDF 930KB](333)

Abstract:
The effects of Yttrium on the microstructure of Ti-23Al-25Nb alloy have been studied by OM,XRD,XRF,SEM,EPMA and TEM.The results show that the microstructure of two casting alloys is orthorhombic phase(O-phase).Yttrium has obviously refined the grain size of the alloy,where the Ti-23Al-25Nb grain size within a range of 400-600μm,and the Ti-23Al-25Nb-0.36Y grain size within a range of 40-100μm,refined to about 6-8 times.By BSE and TEM,it is found that the Y2O3 lies in the interior of grains and along grain boundary in Ti-23Al-25Nb alloy.Base on the forming mechanism of O-phase and theory of grain refinement,the effects of Yttrium on the refinement process of O-phase have been analyzed.

Studying to Metal Image Segmentation

CAO Li, SHI Zhong-ke

2006, 26(1): 11-15.

[Abstract](1484) [PDF 660KB](199)

Abstract:
With the requirement of metal tissue analysis increasing,metal image processing has become an important field of image processing.Combining with some characters of metal image,metal image segementation was analyzed by traditional methods and a method based on maximum entropy principle.Furthermore,a new method of metal image edge detection was presented by binary image.The results of contrastive experiments indicated that the method based on maximum entropy principle could obtain better metal binary images and the edge detection method in the paper could get continuous and closed grain boundaries.These boundaries can provide reliable foundations to next metal image processing.

Effect of Direct Current Eiectiric Fieid on Structure of Directionally Solidified Al-4.5%Cu Alloy

XU Qian-gang, WU Bao-lin, WAN Gang, ZHAO Yu-hua, WANG Hong-shun

2006, 26(1): 16-19.

[Abstract](1541) [PDF 1153KB](285)

Abstract:
Variation of the structure of directionally solidified Al-4.5%Cu alloy under direct current electric field were studied.The results show that electric current facilitates directional dendrite solidification in Al-4.5%Cu alloy.Increase in electric current density refined the secondary dendrites evidently and the content of θ(CuAl2) phase in the directionally dendrite solidification microstructures increased.The experimental results were discussed in terms of the effects of electric current on temperature gradient and solute re-distribution.

Study on Carbon Balls in Anode Nozzle of DC Arc Jet Plasma Torch

CHEN Rong-fa, ZUO Dun-wen, LI Duo-sheng, XIANG Bing-kun, ZHAO Li-gang, WANG Min

2006, 26(1): 20-24.

[Abstract](1469) [PDF 702KB](384)

Abstract:
The free-standing diamond film wafers with different thickness were prepared by high power DC arc plasma jet CVD method.The question of carbon balls in anode nozzle was one of the most serious problems during the deposition.The reasons were firstly studied with theoretical analysis and experimental investigation.Structures and compositions of the carbon balls were examined by Raman spectra.The results indicated that carbon balls were consisted of three layers,which were diamond film,mixed layer and outermost graphite.Effect on the formation of carbon balls was studied in detail by methane concentration,temperature of cooling water,local high temperature of discharge arc,surface finish of anode nozzle.The ways to solve this problem are presented.

Study of Foil Thickness Uniformity Prepared in EB-PVD

HAN Jie-cai, LI Xiao-hai, CHEN Gui-qing, MENG Song-he

2006, 26(1): 25-28.

[Abstract](1284) [PDF 414KB](244)

Abstract:
A mathematical model of foil thickness distribution used for electron beam physical vapor deposition technology is presented by taking the evaporation on big and rotary substrate and improvement of foil thickness uniformity into consideration.The theory of small plate evaporation source under the condition of vacuum evaporation is used in this model.Using this model,qualitative analysis of foil thickness relative to different crucible position is done.The relative position between crucible and substrate is optimized in fact so that the foil thickness deposited on the substrate is the considerably uniform.At last,the theoretic foil thickness and experimental foil thickness tend to be identical through presenting K.It is shown that mathematical model is reasonable.

Effect of the Atomic Oxygen of Space Environment on Properties of Kapton/Al Film

CHU Wen-yi, YANG Shi-qin, HE Shi-yu, LI Dan-ming

2006, 26(1): 29-31,35.

[Abstract](1358) [PDF 909KB](325)

Abstract:
In order to simulate the atomic oxygen effects in space environment on thermal control coatings,the changes in mass loss,optical properties,surface morphology and surface roughness of Kapton/Al films were investigated in conditions of a fixed density of atomic oxygen beam for different time.The experimental results showed that the mass loss of atomic oxygen effects is in proportion to the irradiation time.The solar absorptance changed obviously,while the emittance has little change after irradiation.The roughness of irradiated surface of samples is an important factor to influence the solar absorptance.With increased irradiation time,the surface roughness and solar absorptance are increased.

Study on Mechanism of Polystyrene Powder in Selective Laser Sintering

XIE Xiao-lin, WANG Yun-ying, MENG Jiang-yan, FAN Hong-qing, LI Zhi-peng

2006, 26(1): 32-35.

[Abstract](1385) [PDF 261KB](311)

Abstract:
In this paper,the mechanism of polystyrene powder in selective laser sintering and the method of improve its properties are investigated.The experimental results show that an addition of inorganic filler can improve the properties of polystyrene powder in selective laser sintering,and cooperative effect results from several additional inorganic filler is evident.

Application of Diels-Alder Reaction and Phenylsilylene in Synthesis of Heat-Resistant Polymer

ZHANG Fan, HUANG Peng-cheng

2006, 26(1): 36-39.

[Abstract](1406) [PDF 213KB](226)

Abstract:
Two polymers containing phenyleneethynylene or 2,7-diethynylenenaphthalene and phenylsilylene in their main chain were synthesized.The influences of phenylsilylene on the melting point and solubility of the polymers as well as their curing reactions were studied.The results show that the introduction of phenylsilylene can reduce the melting point and increase the solubility of the polymer and the Diels-Alder reaction between-ph-C≡C-and-C≡C-can produce rigid fused benzene rings in the polymer after curing.This principle can be used to synthesize novel highly heat-resistant polymer with good processability or be used to modify highly heat-resistant polymer such as polyimide.

Influence of Preceramic’s Concentration, Pyrolysis Temperature and Inert Filler on Pyro-joining of Ceramic Materials via Preceramic Silicone Resin

SUO Jun, CHEN Zhao-hui, ZHENG Wen-wei, HAN Wei-min

2006, 26(1): 40-45.

[Abstract](1159) [PDF 1029KB](194)

Abstract:
The joining of graphite,ceramic SiC and Cf/SiC composites via preceramic silicone resin(SR) at high temperature(800~1400℃) is studied.The curing and pyrolysis process of silicone resin,solution concentration,pyrolysis temperature and inert filler are especially discussed.The results show that the curing process of SR is accomplished by Si-OH.Different influences of solution concentration and pyrolysis temperature appear according to different be-joined.Appropriate amount of inert filler is good for the joining of Cf/SiC composites.

Investigation on Solvent Effect on Silica Fiber/Phenolics Composites Produced by RTM Solution Impregnation Process

WANG Bai-chen, HUANG Yu-dong, LIU Li

2006, 26(1): 46-50.

[Abstract](1407) [PDF 567KB](203)

Abstract:
The effects of different solvent species on resin transfer molding(RTM) solution impregnation process of silica fiber/phenolics composites were investigated.XPS and in-situ electron paramagnetic resonance(EPR) spectra were used to examine the interfacial chemical reaction between silane coupling reagent on silica fiber surface and the components of phenolic resin solution.Resin distribution and interfacial adhesion were evaluated by TGA and interlaminar shear strength(ILSS) measurements.The results show that solvents compete with phenolic resin for the adsorbing sites on the silica fiber.As increase in hydrogen bonding capacity of solvent used in this study,the extent of solvent effect is in the following order: THFacetoneethanol.

Study on the Behavior of Non-Isothermal Crystallization and Melting of the Modificated PA6/Kevlar Fiber Composites

ZHENG Yu-ying, FU Ming-lian, WANG Can-yao

2006, 26(1): 51-54.

[Abstract](1494) [PDF 568KB](223)

Abstract:
Differential scanning calorimetry was used to investigate the effect of polymide6(PA6) grafted Kevlar fiber on the non-isothermal crystallization behavior of PA6/Kevlar fiber composites.The results showed that the non-isothermal crystollization of PA6 was dominated by nucleation while the un-grafted Kevlar fiber played an role of heteregeneous nucleation agent in the process of crystallization of PA6 and increased its Tonsetc and ttotal.The PA6 grafted Kevlar fiber still played the role of heteregeneous nucleation agent in the PA6/Kevlar fiber composites,however,its effect was less than that of the ungrafted Kevlar fiber.This may be ascribed to the improved interfacial adhesion between PA6 and Kevlar fiber in the composites where the movement of PA6 segments are inhibitted.The melting bahavior showed that the join of Kevlar fiber made the temperature and intensity of low-temperature melting peak improved.Kevlar fiber also improved the integration degree of crystal.

Study of Interface Reaction in the Si₃N₄/Al Composite Prepared by Pressureless Infiltration

WANG Yang-wei, WANG Fu-chi, YU Xiao-dong, LI Jun-tao

2006, 26(1): 55-58.

[Abstract](1496) [PDF 582KB](270)

Abstract:
It is significant to study the relationship between the oxidation level of the Si3N4 porous preform and the interface reaction for providing the base of optimizing designation of the Si3N4/Al composite.The preforms with different oxidation level were pressurelessly infiltrated under the same processing conditions.Oxygen content of the preforms,phase constituents,and hardness of the composites were characterized by EDS,XRD instruments and Rockwell hardness tester respectively.The XRD results showed that the Si3N4/Al composite contain Al,Si3N4,AlN and a small amount of Si,Mg2Si,MgO,MgAl2O4.With the increasing oxidation level of preforms,the reaction product of AlN decreased remarkably and MgO increased.More MgAl2O4 were measured from the composite which preform presintered at the higher temperature of 1200℃.The hardness of composite went down with the increasing of the oxidation level of preform.It is an important reason for the reduction of the hardness of composites that the oxide over Si3N4 particles results in the decreasing of replacement reaction between Al-Mg melt and Si3N4.

Design of Ti-Zr-Cu-Ni-Co System Ti-Based Brazing Alloy and Mechanical Properties of TC4 Brazed Joints

CHEN Bo, MAO Wei, XIE Yong-hui, XIONG Hua-ping, CHENG Yao-yong, GUO Wan-lin, LI Xiao-hong

2006, 26(1): 59-62.

[Abstract](1498) [PDF 1064KB](290)

Abstract:
In this paper,a Ti-Zr-Cu-Ni-Co system Ti-based brazing alloy is recently designed.Compared with BПP16 brazing alloy,Zr content in the new brazing alloy is increased to some extent,and the total amount of alloying elements Cu,Ni,and Co is lower than that of elements Cu and Ni in BПP16 brazing alloy.Melting and brazing experiments for TC4 alloy were conducted under the vacuum heating condition of 960℃/10min.The microstructures of the brazed joints were examined under SEM and the compositions of some micro-zones were analyzed through XEDS.The test results of mechanical properties of the brazed joints show that,compared with BПP16 brazing alloy,the impact roughness of the joints brazed with the new brazing foils is increased by 56%,and moreover,the shear strength is also increased by about 20%.

Investigation on Mechanism of Oxygen Gaining Occurring in Droplet Reaction Zone During SAW

LI Xiao-quan, LIU Peng-fei, WANG Guang-yao

2006, 26(1): 63-66.

[Abstract](1264) [PDF 856KB](271)

Abstract:
Using water cooled copper testing device,coupled with series of agglomerate fluxes made by the present laboratory,welding experiments have been conducted to extract the rapid cooled droplets in submerged arc welding.With the help of LECO oxygen-nitrogen analytical instrument,the oxygen and nitrogen contents in droplets have been measured,and scan electron microscope has been applied to explore internal morphology or analyze micro-zone chemical composition so as to discuss mechanism of oxygen gaining occurring in droplet reaction zone.

Microstructures and Mechanical Properties of Friction Stir Welding Joint of 2014 Aluminum Alloy

ZHAO Yan-hua, LIN San-bao, SHEN Jia-jie, WU Lin

2006, 26(1): 67-70.

[Abstract](1483) [PDF 1055KB](347)

Abstract:
Friction stir welding of 2014 Al alloy in 8 mm thickness has been successfully completed.The metallurgy experiment demonstrates that the FSW joint microstructures could be divided into four different regions and the dynamic recrystallization occurs in the weld nugget and the shoulder affected zone(SAZ),which consist of refined,equiaxed grains.The microstructures in TMAZ,in which recovery occurred,consist of highly deformed grains and those in HAZ consist of coarse wattle grains.Mechanical property measurements demonstrate that the peak tensile strength of the joint can reach 361MPa,as much as 78% of the base metal,and the bend strength can reach 76% of the base metal.The fracture analysis shows that the fracture mode of the joints is ductile/brittle mixed fracture.

Effect of Recrystallization on Low-Cycle Fatigue Behavior of DZ4 Directionally-Solidified Superalloy

ZHANG Hai-feng, SHI Hui-ji

2006, 26(1): 71-75.

[Abstract](1474) [PDF 1170KB](303)

Abstract:
Low cycle fatigue failure was investigated on DZ4 directionally-solidified nickel-base superalloy at room temperature.Real-time SEM surface observation was employed.Experiment result reveals that its surface recrystallization layer strongly influences the material performance.All specimens were prepared under condition of shot peening and high temperature annealing,different shot peening pressure specimens have different recrystallization state.High shot penning pressure specimens have clear and straight grain boundaries and the grain size appears to be larger.Recrystallization state seems not only affect the fatigue life,but also the crack initiation pattern and crack initiation life.High shot peening pressure specimens have higher fatigue life comparing to low shot peening pressure specimens,although it is almost half lower as the virgin one.have much lower fatigue life,and SEM Real-time observation reveals that channeling crack initiated at the early stage of fatigue life.High shot peening pressure specimens have higher fatigue life comparing to low shot peening pressure specimens,although it’s almost half lower as the virgin one,and the crack density is also much smaller.Crack initiation life is much longer than those of low shot peening pressure.Low shot peening pressure specimens seems not fully recrystallized,Since the grain boundaries are much fragile which is responsible for high density microcrack initiation,and finally leads to the failure.

Studies on Creep Behavior of Three Dimensional Braiding Composites

LI Dian-sen, LI Jia-lu, CHEN Li, LU Zi-xing

2006, 26(1): 76-80.

[Abstract](1443) [PDF 613KB](344)

Abstract:
The creep of three dimensional braiding composites were studied by creep experiments of specimens under different braiding structure,braiding angle,fiber volume content and loads.The experiment results show that the creep resistant properties of the three dimensional four directional braiding composites are worse than five directional braiding composites.The creep resistant properties can be improved with a lower braiding angle and higher fiber volume fraction.Furthermore,the creep rate is increased with the increasing of load.In addition,it is found that the power function is the best fit equation of creep curve for 3-D braiding composites.

2006 Vol. 26, No. 1