航空材料学报

Effects of Solution Treatment on Microstructures and Properties of Al-Cu-Li-X Alloy

WU Xiu-liang, YUAN Zhi-shan, XIE You-hua, DAI Sheng-long

2009, 29(3): 1-6.

[Abstract](1670) [PDF 1415KB](256)

Abstract:
Solution treatments of 510~530℃ for 40~120 min were applied upon Al-Cu-Li-X alloy,2A97,followed by artificial aging at 165℃ for 18h,and the effects of solution treatment on the microstructures and tensile properties has been investigated by tensile test,OM,SEM,and TEM.The results show that when the solution temperature increased from 510℃ to 530℃,intermediate by 520℃,the tensile strength and elongation of aged alloy tended to decrease.When the solution time increased from 40 to 120min,intermediate by 80min,the yield tensile strength increased,and the elongation got maximum at 80min for aged alloy.Increasing the solution temperature or prolonging the solution time dissolved the soluble particles as AlCuMgZn.Numerous fine precipitates distributed homogeneously in matrix were observed by solution treatment at 520℃ and aging at 165℃.

Study of Magnetic Properties of 2J4 Alloy Deformed by Equal Channel Angular Pressing after Tempering

DU Zhong-ze, WU Lai-zhi, FU Han-guang, WANG Qing-juan, WANG Jing-tao

2009, 29(3): 7-12.

[Abstract](1659) [PDF 799KB](204)

Abstract:
The magnetic properties of 2J4 alloy deformed by the equal channel angular pressing(ECAP) have been studied in different tempering temperature,and were contrasted with those of the cold rolling 2J4 alloy.The results shows that the more the ECAP deformation extent is,the better the magnetic permeability of 2J4 alloy will be,the relation between them is the positive pertinence.The saturation magnetic flux density of 2J4 alloy is the best after four passes ECAP.Moreover,the change of the magnetic performance of 2J4 alloy is very sensitive to the change of tempering temperature.The best magnetic retardation performances are found in the 2J4 alloy,which is rolled with a deformation amount of 85%,along the extruding direction after four passes ECAP deformation.Its coercive force reaches 3.8364 kA/m.The magnetic retardation performance of ECAP 2J4 alloy is better than that of traditional cold rolling 2J4 alloy.The results favors that the fabrication of high performance magnetic material by means of ECAP is feasible.

Preparation of Al/Tb_0.3Dy_0.7Fe_1.95 Magnetostrictive Composites by Powder Sintering Process

JIANG Min-hong, GU Zheng-fei, LIU Xin-yu, CHENG Jun, ZHOU Xiu-juan

2009, 29(3): 13-16.

[Abstract](1611) [PDF 1416KB](284)

Abstract:
Using powder sintering process,Al/Tb0.3Dy0.7Fe1.95 composites were prepared.Dependence of sintering temperature on the microstructure,phases,magnetostriction and mechanical property of composites were investigated.The results show that there mainly are ReFe2 and Al phases in the composites sintered at 600℃.The sintered body has good microstructure.And ReFe2 phases reduce accordingly with the increasing of sintering temperature.There are mainly different impurity phases in the composites sintered at 1200℃.With the increasing of sintering temperature,magnetostriction and compressive strength of composites decrease evidently.When the sintering temperature is at 600℃,the magnetostriction and the compressive strength of the composites are 405×10-6and 61.71 MPa,respectively.But it is a pity that the Al/Tb0.3Dy0.7Fe1.95 composites are still fragile.

Microstructure and Property of SiC_f-reinforced Titanium Based Composite Joint Using Ti-Zr-Cu-Ni-Co Brazing Filler

CHEN Bo, XIONG Hua-ping, MAO Wei, CHENG Yao-yong, GUO Wan-lin

2009, 29(3): 17-22.

[Abstract](1550) [PDF 2005KB](207)

Abstract:
Ti-Zr-Cu-Ni-Co brazing filler was used for joining SiCf/β21S titanium matrix composite.The vacuum brazing test of SiCf/β21S was carried out and the mechanical property was investigated.The corresponding joint microstructure and interfacial were discussed.The results indicated that,under the vacuum heating condition of 960℃/10min,the shear strength of the SiCf/β21S joints is 157.8MPa.However,the joint strength under the brazing condition of 960℃/10min/5MPa is increased to 291.2MPa.Because of existence of 5MPa pressure,the latter joints contain less amount of brazing defects and brittle compounds of Ti(Zr)-Cu(Ni,Co) than the former,which is the main reason that the two average shear strength values have a great difference.

Effect of Oxidation Time on Micro-arc Oxidation Ceramic Coatings Formed on 7A55 Aluminium Alloy

LI Zhong-sheng, WU Hu-lin, PAN Fu-sheng, ZHANG Long-ping, HE qing-bing

2009, 29(3): 23-26.

[Abstract](1579) [PDF 519KB](321)

Abstract:
Ceramic oxide coatings were formed on 7A55 aluminium alloy surface by micro-arc oxidation(MAO) at the constant current density of 6A/dm2 in Na2SO3-NaOH-(NaPO3)6 solution.The effects of oxidation time on surface microphologies,thickness and phase composition of the micro-arc oxidation coatings were investigated.The results indicate that with increasing oxidation time,anodic voltage increases gradually and the number of micropores of the MAO coatings decreases while the size of the micropores increases with constant electrical parameters(i=6A/dm2,D=30% and f=1000Hz).The thickness of the coatings increases lineally with oxidation time increasing.The MAO coatings is mainly composed of γ-Al2O3.

Effects of Hot Deformation Conditions on Flow Stress and Microstructure of Ag-contained Al-Cu-Mg Heat-Resistant Aluminum Alloy

LIU Xiao-yan, PAN Qing-lin, LU Cong-ge, LI Wen-bin, ZHANG Xin-ming, YIN Zhi-min

2009, 29(3): 27-32.

[Abstract](1634) [PDF 848KB](223)

Abstract:
The behavior of the flow stress of Ag-contained Al-Cu-Mg heat-resistant aluminum alloy during hot compression deformation was studied by thermal simulation test.The temperature and the strain rate during hot compression were 340~500℃,0.001~10s-1,respectively.The results show that the flow stress increases with increasing the strain rate,and decreases with increasing the deforming temperature.The flow stress of the alloy during hot compression deformation can be described by constitutive equation in hyperbolic sine function with the hot deformation activation energy 196.27 kJ/mol,and can also be described by a Zener-Hollomon parameter.Only elongated grains vertical to compression direction were observed in the alloys deformed at low temperature or high strain rate.With increasing deformation temperature or decreasing strain rate,the elongated grains coarsed and recrystallization grains were also observed,indicating that the main soften mechanism of the alloy transformed from dynamic recovery to dynamic recrystallization.The suitable hot rolling temperature is 380~460℃ and the strain rate is 0.1~10s-1.

Investigation of Effect of Tensile Property and Fracture Behavior of Pure Aluminum during ECAP

WANG Jin-feng, BAI Pu-cun, ZHANG Xiu-yun, HOU Xiao-hu, REN Yong-gang

2009, 29(3): 33-38.

[Abstract](1569) [PDF 1825KB](334)

Abstract:
The pure Al was pressed continuously by equal channel angular pressing;the dislocation reinforcement and fracture mechanism are studied by micrographs of dislocation and tensile fracture surface of the pure Al.The TEM results show that the shear deformation makes dislocation slips and refines grain,and makes the yield strength and the ultimate tensile strength increase by 38.5% and 24.0% respectively after four passes by ECAP,Fracture mechanism presents typical intergranular fracture.

Numerical and Experimental Research on Micro-damage of SiC_p/A356 Composites

YANG Zhi-yong, HAN Jian-min, LI Wei-jing, CHEN Yue, WANG Jin-hua

2009, 29(3): 39-44.

[Abstract](1465) [PDF 936KB](242)

Abstract:
Macroscopically mechanical behaviors were closely related with the micro-damage mechanism of SiC particle reinforced aluminum matrix composites.With the temperature increasing,the mechanical properties of the composites decreased significantly,the reason of which was the micro-damage mechanism of the composites was different at different temperature.The unit cell model for the SiCp/A356 composites was established which consists of a spherical SiC particle and aluminum matrix.On the basis of the model,the simulation study on the micro-damage mechanism of the composites was carried out.The micro-damage mechanism of the composites from the finite element simulations was consistent with the results from the experimental investigations.It can be concluded that the crack initiation mechanism of the composites at room temperature was mainly tear of the matrix and fracture of SiC particles mainly;while the mechanism of the composites at high temperature was SiC particle debonding from the matrix and tear of the matrix.

Influence of Processing Parameter on Microstructure and Forming Characterizations of Ni-Cr Cladding Formed by Plasma Surfacing Processes

BI Xiao-qin, HU Xiao-li, WANG Jie

2009, 29(3): 45-49.

[Abstract](1549) [PDF 843KB](249)

Abstract:
The Ni-Cr cladding was coated on the 40Cr alloy by the PTA(plasma Transferred arc) surfacing process.The influence of processing parameter on the microstructure and forming characterizations of the cladding were analyzed.The results indicate that the cladding is well bonded with the matrix and the interface consists of the regular dentritic crystal.The microstructures vary from the thick dentritic crystal in the middle of the cladding to fine equiaxed crystal near the top of the cladding.With the increase of power,the crystals of the cladding are fined under the same scan velocity.The ill-bonding occur in the interface under the lower power and the higher scan velocity,and the crack will appear in the cladding under the higher power and the lower scan velocity.The content of Ni and Cr come into changing evidently in the interface.The cladding with the lower ratio of dilution is acquired under the condition of 2.0kW and 12.0mm/s in this paper.

Effect of Deposition Temperature on Composition and Morphology of TiB₂ Coating

CHEN Da-jun, WU Hu-lin, ZHANG Long-ping, SUN Cai-yun, LI Zhong-sheng, HE Qing-bing

2009, 29(3): 50-54.

[Abstract](1614) [PDF 1378KB](201)

Abstract:
The TiB2 coating on the surface of Graphite was prepared by CVD method in TiCl4-BCl3-H2-Ar system.The influences of deposition temperature on phase composition,deposition rate,microstructure and surface morphology of TiB2 coating were studied.The experimental results show that the coating is composed of TiB2.With the increase of deposition temperature the deposition rate increases.The micro hardness of coating increases firstly and reaches its maximum value at 950℃ and then decreases;The particle size enlarges obviously with the rising of temperature,the dense structure and the suitable particle size of TiB2 coating can be deposited between 900℃ and 950℃.The depositing mechanism of CVD-TiB2 coating was analyzed.

EB-PVD Thermal Barrier Coatings with Micro Laminated Structure

MU Ren-de, HE Shi-mei, HE Li-min, Xu Zhen-Hua

2009, 29(3): 55-60.

[Abstract](1855) [PDF 649KB](315)

Abstract:
Thermal barrier coatings(TBCs) with micro laminated structure were fabricated by interrupted electron beam physical vapor deposition(EB-PVD).Using scanning electron microscope(SEM),the structure and crystal morphology of coatings were observed and analyzed.And the thermal diffusivity of coatings was measured by laser flash method.Additionally,the oxidation dynamic characterizations of coatings were investigated via weight gain in isothermal oxidation test and the diffusion of elements in coating systems were analyzed by energy dispersive spectroscopy(EDS) after oxidized.The results show that TBCs prepared by interrupted EB-PVD process presents clear layered characteristic.The columnar crystal structure,which particularly owned to EB-PVD coatings,is periodically disrupted.However,columnar characteristic is still preserved in each layer and the crystal grains become shorter and finer.The inter-layer interface and finer grain of micro laminated TBCs reduce the phonon mean free path,which mainly responsible for the 20% to 30% reduction of thermal diffusivity than that of the conventional deposited value in the temperature range of 25~1200℃.The weight gain rate of micro laminated TBCs is obviously lower than its conventional deposited counterpart.The main reason for this phenomenon is likely that interface and finer grain weaken or prevent the diffusion of O,Al,Ni,Cr,etc.elements.

Microstructure and Properties of Alumina Coating Deposited on Titanium by Cathodic Microarc Method

JIN Qian, XUE Wen-bin, LI Xi-jin, ZHU Qing-zhen, WU Xiao-ling

2009, 29(3): 61-65.

[Abstract](1517) [PDF 1454KB](230)

Abstract:
An alumina coating was prepared on titanium by cathodic microarc deposition in Al(NO3)3 ethanol solution.The morphology,composition and phase constituent of the alumina coating were analyzed,and the oxidation behavior,thermal shock resistance and corrosion resistance were determined.Moreover,the mechanism of cathodic microarc deposition was also discussed.The coating is composed of γ-Al2O3 and little α-Al2O3 phases.The coating contains a little titanium element,which confirms that titanium substrate near the coating/titanium also takes part in the deposition and sintering process of coating under cathodic microarc discharge.After 100 times thermal cycling of 700 ℃ coated sample quenching into water,the coating still remains a good adhesion to titanium substrate.In addition,the oxidation rate of the coated titanium is reduced about 4 times under 700 ℃ isothermal oxidation test.

Characteristics of Hot Compression Deformation for In-situ TiB₂/6351 Composites

GUO Sheng-li, LI De-fu, CHEN Dong, WANG Hao-wei

2009, 29(3): 66-70.

[Abstract](1497) [PDF 1420KB](185)

Abstract:
The characteristics of hot compression deformation for in-situ TiB2/6351 composites have been studied in the different temperatures and strain rates using Gleeble-1500D system and the microstructures of compression samples were observed by transmission electron microscopy(TEM) and optical microscope.The results show that flow stress is affected obviously by strain rate and deformation temperature.Flow stress decreases with deformation temperature rising at constant strain rate,and increased with strain rate falling at constant deformation temperature.The flow deformation behavior mainly includes working hardening,dynamic recovery and dynamic recrystallization,and the associated microstructures represent dislocation networks and dislocation cell structures with high density dislocations,the subgrain structures and equiaxed grains.The dislocation density domain in the matrix was formed around the reinforced particles at lower deformation temperature and strain rate,and reduced with deformation temperature increasing.At higher strain rate,the interface separated even the particle itself cracked.

Structure and Properties of Vulcanized A crylonitrile-butadiene/Phenolic Resin/Hindered Phenol AO80 Damping Rubbers

ZHAO Yun-feng, ZHANG Ji-hua, YOU Shao-xiong, HE Li-jun, ZHAN Mao-sheng

2009, 29(3): 71-77.

[Abstract](1588) [PDF 2135KB](514)

Abstract:
3,9-bis[1,1-dimethyl-2{β-(3-tertbutyl-4-hydroxy-5-methylphenyl)propionyloxy}ethyl]-2,4,8,10-tetraoxaspiro-undecane(AO80) and the phenolic resin(PR) were added into the acrylonitrile-butadiene rubber(NBR) to prepare the vulcanized NBR/PR/AO80 rubbers.The structures of vulcanized rubbers were characterized by DSC,FTIR and SEM.And their damping and mechanical properties were investigated in detail.The results showed good compatibility of AO80 in the blend system,which had a single peak in the temperature spectrum of dynamic mechanical properties.With the content increase of AO80,the damping peak of vulcanized rubber enhanced.However,the mechanical properties increased,and then decreased with the content increases of AO80.In contrast with NBR/PR rubbers,NBR/PR/AO80 rubbers possessed almost the same damping temperature ranges and higher damping peaks.Therefore,we believed that it would be a kind of respectively high-damping rubber.

Effects of PIP-SiC Coating of SiC Fiber on Mechanical Properties of 2D-SiC_f/SiC Composites

LIU Hai-tao, CHENG Hai-feng, WANG Jun, ZHOU Wang, TANG Geng-ping, ZHENG Wen-wei

2009, 29(3): 78-82.

[Abstract](1552) [PDF 878KB](328)

Abstract:
SiC coating of SiC fiber was prepared by Precursor Infiltration Pyrolysis(PIP) process using low concentration precursor solution,and effects of infiltration pyrolysis times on coating morphology were studied.The results show that the continuous and compact coating can be gained by three times of infiltration pyrolysis process using 10t%(mass fraction)PCS solution.The 2D-SiCf/SiC composites were fabricated by Hot Pressing-Precursor Infiltration Pyrolysis process using SiC fiber cloth containing SiC coating.It is found that the flexural strength of composites reached the maximal value by three times of infiltration pyrolysis process,and the flexural strength increased about 50%,from 163.5MPa without coating treatment to 245.9MPa.The research indicates that the SiC coating can decrease the damage of SiC fiber,and the interface also can be improved,which makes the mechanical properties enhance obviously.

Study on NH₃ Plasma Surface Modification of Kevlar Fabric

ZHOU Zheng-gang, LI Min, JIANG Shi-cai

2009, 29(3): 83-87.

[Abstract](1477) [PDF 799KB](344)

Abstract:
The Kevlar-49 fabric was modified with NH3 plasma under the conditions of 74.9Pa/113W/14.3min.The results show that the interfacial shear strength of the Kevlar-49/3234 epoxy composites is improved by 26.6% than that of untreated,and the T-peel strength by 22.9%.The mean surface roughness is significantly enlarged and the contact angle with water is lowered.SEM micrographs of T-peel fracture surface of Kevlar-49 S500/3234 epoxy composite made from NH3 plasma treated fibers showed that the fracture mode was fiber skinned.

Tensile Properties of Twist Low Angle Boundary of DD6 Single Crystal Superalloy

SHI Zhen-xue, LI Jia-rong, LIU Shi-zhong, ZHAO Jin-qian

2009, 29(3): 88-92.

[Abstract](1719) [PDF 2050KB](270)

Abstract:
The transverse tensile properties and fracture behaviour of the twist low angle boundary of DD6 single crystal superalloy were investigated at 760℃,850℃ and 980℃.The transverse tensile strength of the specimens with the same twist LAB decreases with the increasing of temperature.When the LAB of the specimen is 10.8° at 760℃,6.4° at 850℃ and 3.8° at 980℃ respectively,intergranular rupture can be observed and the tensile strength decreases.The intergranular rupture mode makes the tensile plastic of the specimen decrease.

Mechanical Properties of SiC/SiC Composites

YU Xin-min, ZHOU Wan-cheng, LUO Fa, ZHENG Wen-jing

2009, 29(3): 93-97.

[Abstract](1808) [PDF 645KB](256)

Abstract:
2.5 dimensional SiC/SiC composites with pyrocarbon interlayer were fabricated by low pressure chemical vapor deposition(LPCVD).Effects of residual pores and interlayer thickness on mechanical properties of fabricated SiC/SiC composites were investigated.The flexural strength of the composites is mainly affected by the micro-pores between filaments instead of the macro-pores between yarns.Strength increases with the decrease of the amount and size of micro-pores.When the porosity is below 27%,the further decrease of the porosity does not change the amount and size of micro-pores and hardly contributes to the strength.The existence of a pyrocarbon interlayer of 90nm thickness increased composite strength from 174 MPa to 305 MPa,and changed the fracture behavior from catastrophic fracture to non-catastrophic fracture.The further increase of interlayer thickness results in fiber damage which reduces the mechanical properties of the composites.The strength of the composites with 180nm and 310nm thick interlayers is 274 MPa and 265 MPa,respectively.Their amount of fiber pullout is small and the fracture behaviors are similar to catastrophic fracture.

Effect of Elastic Modulus of Adhesives on Stress Distribution in Weld-bonded Joints

YOU Min, YAN Jia-ling, ZHENG Xiao-ling, HE Ai-ping, ZHU Ding-feng

2009, 29(3): 98-101.

[Abstract](1502) [PDF 1004KB](262)

Abstract:
The effect of the elastic modulus of adhesives on the stress distribution in aluminumalloy weld-bonded single lap joint under loading was investigated using the elastic-plastic finite element method(FEM).The results showed that the stress distribution in the overlap zone was more uniform as the elastic modulus of the adhesive increased along the horizontal plane and the peak stresses occurred adjacent to the adhesive layer decreased evidently,but the peak stresses in mid-bondline near the free end of the lap zone was increased.At the plane 0.05 mm away from the mid-bondline,the peak stresses at the point corresponding to the center of the spot nugget at the joint decreased greatly when the elastic modulus increased.

Relationship between Surface Length and Inside Length of Fatigue Crack in Ultra-high Strength Steel

WANG Miao-miao, ZENG Yan-ping, WANG Xi-shu, XIE Xi-shan

2009, 29(3): 102-106.

[Abstract](1434) [PDF 1931KB](250)

Abstract:
Ultra-high strength steel makes advancement incessantly with development of aeronautical industry.However,its sensitivity to the flaw increases with increasing in strength level.Non-metallic inclusion as one of the inevitable flaws must influence the performance,especially fatigue performance,of ultra-high strength steel.In-situ fatigue tests with special designed SEM have been conducted to trace the whole process of crack initiation and propagation induced by AlN inclusion in ultra-high strength steel under low-cycle fatigue load.The strong linear between the surface length and the inside length of fatigue crack was gained.The inside length can be calculated based on the surface length of fatigue crack detected in material or structure and the residual life can be estimated.

Detecting Impact Damage-Resistance Change in Carbon Fiber/Epoxy-Matrix Laminate by Ultrasonic F-scan

XIE Xiao-lin, LIAO Jia, FAN Hong-qing, WANG Gao-chao, QUAN Hong-ying, LI Zhi-peng

2009, 29(3): 107-110.

[Abstract](1595) [PDF 328KB](317)

Abstract:
Impacted carbon fiber /epoxy-matrix laminates were detected by ultrasonic F-scan,their resistance were measured before and after they had been impacted separately.The status of impacted laminates were analyzed through synthesizing impact energy,resistance change and ultrasonic F-scan graph.The results show that ultrasonic F-scan can ensure impact damage energy threshold value of carbon fiber /epoxy-matrix laminates.The resistance of laminates can be changed after they have been impacted,but there are damage in them only after they have been impacted by exceed threshold energy.So,ultrasonic F-scan can improve veracity of detecting impact damage in laminates by resistance measurement.

2009 Vol. 29, No. 3