航空材料学报

Effect of Temperature on Cyclic Fatigue and Final Fracture Mechanism of 2E12 Aluminum Alloy

YANG Sheng, YI Danqing, YANG Shoujie, ZHONG Li

2007, 27(6): 1-5.

[Abstract](1414) [PDF 1404KB](400)

Abstract:
The effect of temperature on cyclic fatigue life and fracture mechanism on 2524-T4 aluminum alloy was studied by cyclic fatigue test,SEM and TEM.The results showed that temperature had a detrimental influence on cyclic fatigue life,the cyclic fatigue strength of 106 cycles at elevated temperature(100℃) decreased 30MPa than the fatigue strength at cryogenic temperature(-55℃).Temperature changed the relation of dislocation,second-phase particles and grain boundary,the fracture surface at cryogenic temperature showed the crystallographic fracture.The dominant deformation process at ambient and elevated temperatures was a combination of predominantly transgranular and local intercrystalline fracture mechanism.

Effects of Low Angle Grain Boundaries on Stress Rupture Properties of Single Crystal Superalloy DD6

ZHAO Jinqian, LI Jiarong, LIU Shizhong, YUAN Hailong, HAN Mei

2007, 27(6): 6-10.

[Abstract](1592) [PDF 1440KB](386)

Abstract:
The effects of low angle grain boundaries(LABs) on the stress rupture properties of second generation single crystal superalloy DD6 were investigated at 800℃,850℃ and 900℃.The stress rupture properties of DD6 with LABs tended to decrease with angle increasing,and were rather low when the angles of LAB were relatively larger.Meanwhile the stress rupture properties of DD6 alloy with [001] orientation were superior to those of the alloy with LABs.When the angles of LABs were relatively lower,the stress rupture properties of DD6 with LABs were lower than those of the alloy with [001] orientation at the condition of 800℃;however,the stress rupture properties of DD6 with LABs approached quantitatively to those of the alloy with [001] orientation at the conditions of 850℃ and 900℃,indicating that the effects of LABs on rupture properties decreased with temperature increasing.

Research on Additional Plastic Deformation of 316L Stainless Steel under Ratchet and Creep Loading

XU Yinjie, CAI Lixun

2007, 27(6): 11-15.

[Abstract](1454) [PDF 593KB](261)

Abstract:
A series of uniaxial experiments for 316L stainless steel were performed under ratchet and creep loading.The material's plastic deformation behavior and the deformation level were analyzed.The research found that the deformation behavior under ratchet and creep loading was somewhat similar;but at identical load time,the deformation caused by creeping was higher than that by ratcheting.Under continual stress loading,the experiment relationship between additional plastic deformation and the stress showed a bulge parabolic pattern.And finally,a constitutive equation to describe this regular pattern was proposed.

Numerical Simulation of Forming in Spray-Casting Clad Roll

WANG Yu, CUI Chengsong, LI Qingchun, ZHANG Guoqing, WANG Wuxiang

2007, 27(6): 16-20.

[Abstract](1430) [PDF 427KB](192)

Abstract:
Through numerical simulation,a shape mathematic model of clad rolls using a coordinate tracing strategy was established to calculate the shape and dimensions of the clad rolls at various spray times and studied the influences of processing parameters.The research results show the shapes of the clad rolls are influenced dramatically by the traveling speed and diameter of the mandrel.However,the influence of rotating speed of the substrate and spray distance on the shape of the clad rolls is rather small.

A Study of Distribution Characteristic and Parameter Analysis of Pre-Corrosion Fatigue Life

HE Xiaofan, LIU Wenting, WANG Zhongbo, YANG Hongyuan, WANG Lei

2007, 27(6): 21-26.

[Abstract](1454) [PDF 1844KB](235)

Abstract:
Pre-corrosion is the most important factor which influence the safety and economics for aircraft structures seriously.To study the influence of pre-corrosion on the fatigue life,the fatigue life of corroded 30CrMnSiNi2A and LC4CS component stimulated specimen were tested under random loading.The fatigue life followed the logarithmic normal distribution or the two-parameter Weibull distribution by the probability regression method.The distribution parameter was estimated with the MLE,and the standards variation of the logarithmic fatigue life was weak-correlation with the pre-corrosion time,and the slope of the Weibull distribution was constant.

Properties of a Cu-Cr-Nd Alloy Treated by Cold-Deformed and Aged

YU Xiaoqing, ZHANG Meng, GUO Shouhui

2007, 27(6): 27-29.

[Abstract](1390) [PDF 466KB](183)

Abstract:
Cu-0.8Cr-0.1Nd(wt%) alloy was cast by median frequency vacuum induction furnace,afterward treated by solid solution,cold-deformed and aging.The microstructure,microhardness and conductivity in each process were investigated by optical microscopy,microhardness tester,and conductivity tester.The results indicate that the adding of Nd can obviously purify the Cu-matrix and refine its grains.With an increase of time of aging,the microhardness of Cu-0.8Cr-0.1Nd alloy first increased,then decreased,however the more cold-deformed of the alloy,the lower hardness was.Conductivity of the alloy after different cold-deformation increased notably,and then went smoothly.But the more the cold-deformed of the alloy,the higher conductivity it was.

Effect of Copper Minor Addition on Glass Forming Ability and Soft Magnetic Properties of FeCoNbSiB Alloy

JIA Yuanzhi, WEI Zunjie, MA Mingzhen, ZENG Songyan, WANG Wenkui

2007, 27(6): 30-34.

[Abstract](1437) [PDF 1471KB](222)

Abstract:
A FeCoNbSiBCu bulk metallic glass(BMGs) was prepared using a commercial Fe-B alloy.The effect of minor Cu addition on the glass forming ability of Fe36Co36Nb4Si4.8B19.2 alloy was studied by differential scanning calorimetry(DSC),X-ray diffraction(XRD),scanning electron microscopy(SEM) and energy dispersive spectrum(EDS).The results show that the glass forming ability of Fe36Co36Nb4Si4.8B19.2 alloy is improved by the addition of 0.5at%～0.7at% copper.Magnetic properties of the as cast(Fe36Co36Nb4Si4.8B19.2)100-xCux(x=0,0.5,0.6,0.7) BMGs were studied using Vibrating Sample Magnetometer(VSM).It is found that the magnetic properties of the alloy are improved with the addition of 0.5at% copper.

Microstructure of Cool-Drawing Austenitic Stainless Steel Wires Used for Metal Rubber

DONG Xiuping, LIU Guoquan, YANG Jianchun, BAI Hongbai

2007, 27(6): 35-39.

[Abstract](1420) [PDF 934KB](379)

Abstract:
By the means of OM,SEM,TEM and EBSD,the microstructures of cool-drawing austenitic stainless steel wires used for metal rubber were studied.The results showed that the microstructures of this steel wires were made up of α′martensite phase,presenting twin and dislocation substructures,and residual austenite phase which was refined into micron dimension.The results also presented that there were so many shuttle-shaped micro holes in this steel wires,lugging along drawing axis and cored by the hard particles second-phase.The further investigation indicates that the Cr17-Ni7 cool-drawing austenitic stainless steel wires were more applicable to use for the high-damp metal rubber.

Impact Toughness and Fracture Characteristics of Linear Friction Welded TC4 Joint

MA Tiejun, ZHANG Xuejun, YANG Siqian, ZHANG Yong, ZHANG Yunxia

2007, 27(6): 40-44.

[Abstract](1392) [PDF 996KB](468)

Abstract:
Based on the optimum parameters obtained from prevenient experiments,the linear friction welding(LFW) experiment of TC4 titanium alloy was carried out with homemade XMH-160 LFW machine.It was found that all the impact test specimens cracked along the parent metal of TC4 alloy after impact test.The macroscopic and microscopic characteristics of impact fractures were observed,and the structure features of the joints were analyzed.The results show that the superfine structure of weld contributes to the higher notched bar impact strength of joint than that of the parent metal.

Experimental Research on Surface Reinforcement Mechanism Introduced by Coupling Effect of Cutting Forces and Heat

LONG Zhenhai, ZHAO Wenxiang, WANG Xibin

2007, 27(6): 45-49.

[Abstract](1425) [PDF 1099KB](252)

Abstract:
HSC(High Speed Cutting) of ultra-high strength steel was conducted in a design of statistic analysis to investigate the coupling effect of mechanical load and thermal load on the surface quality of workpieces.The experimentation demonstrated that the HSC machined surfaces could exhibit significant changes in the surface quality,such as low surface roughness(Ra0.4μm),free of micro-cracks,and reasonable residual stress profiles.The micro-hardness on the surface and sub-surface layer was remarkably increased,the maximum compressive residual stress value was dramatic increased and the compressive residual stress could notably expand to 0.35 mm beneath the machined surfaces.This study indicated that the properly controlled HSC process could be used as a high efficient surface strengthening method which could significantly increase the workpiece’s microstructure properties and service performances with high material remove rate.

In Situ Corrosion Monitoring of Aeronautic Aluminum Alloy LC4 in Acidic Medium

MENG Lin, HE Yedong, ZHANG Wei, YAO Hongyu, XIE Mingli

2007, 27(6): 50-54.

[Abstract](1350) [PDF 529KB](163)

Abstract:
The capacitance measurement method was introduced,which could be used to monitor in situ the corrosion of aluminum alloy LC4 in CH3COOH solutions.The capacitance change of LC4 after anodizing in CH3COOH solutions could be divided three stages.During the slowly risng course of capacitance,the anodic film still maintained the uniformity and compactability;during the quickly rising course of capacitance,the anodic film became porous;and during the drastic oscillation course of capacitance,the anodic film had disappeared completely.In addition,the variation of impedance-frequency spectroscopy with the time measured by LCR number bridge was consistent with that of the EIS result.

Effects of Oxidation Time on Micro-Arc Oxidation Coating of MB8 Magnesium Alloy

ZHAO Qing, HU Yong, DU Nan

2007, 27(6): 55-58.

[Abstract](1516) [PDF 1001KB](245)

Abstract:
The effects of oxidation time on the density,thickness and corrosion resistance of the micro-arc oxidation coatings of MB8 magnesium alloy were investigated.The changes of the micro-topography,component and structure of the coatings with different oxidizing periods were analyzed.The results show that the coating thickness increases with the prolonged oxidation time,but the coating surface gets rough.The corrosion rate of the coating is lowest when the appropriate oxidation time is 10min.Initially the content of the micro-arc oxidation coating is mainly composed of cubic structure MgO,with the oxidation time prolonged,both Mg2(SiO4) with orthorhombic crystal structure and Mg(PO3)2 with monoclinic crystal structure increase gradually in the coating.

Influence of Resin Mixing Process on the Properties of BMI Resin and Prepreg

ZHANG Baoyan, LI Min, CHEN Xiangbao

2007, 27(6): 59-63.

[Abstract](1457) [PDF 780KB](340)

Abstract:
Slurry mixing process was used to prepare modified polyetherketone(PEK-C) toughened BMI resin,and the properties of prepared BMI resin and prepreg were investigated and compared to those from traditional hot melt mixing process.Results indicated that the BMI resin and prepreg prepared from slurry mixing process had good stickiness and storage stability,and the room storage life of prepared prepreg was at least 3 months by determining both stickiness and mechanical properties,while the stiff prepreg without stickiness prepared with the resin from traditional hot melt mixing process had only 20 day room storage life by determining mechanical properties.The prepreg processing temperature was lowed 30～40℃ by using slurry mixing resin.The change of resin mixing process had no influence on mechanical properties and heat resistance of composite.

Preparation of Silicon Carbide Ceramic by Injection Molding and Precursor Pyrolysis

ZHANG Yong, HE Xinbo, QU Xuanhui, ZHAO Zhen, KONG Xianglei

2007, 27(6): 64-68.

[Abstract](1429) [PDF 614KB](159)

Abstract:
Package boxes of Kovar were fabricated by ceramic injection molding process starting with powders of SiC,BC4,C and a kind of wax-based polymer was selected as binders.When the powder solid loading was 52vol%,the optimal injection temperature was at 160~170℃ and injection pressure was under 100~120MPa.Two steps of solvent debinding and thermal debinding was set up to decompose the binder.The density of debinded green was increased to 1.75g/cm3 by polycarbosilan(PCS) precursor infiltration.After being sintered under argon atmosphere for 1h at 2100℃,the boxes with density of 3.11g/cm3 and relative density of 97% could be produced.

Absorbing Properties of Resistive Capacitive FSS Absorbers

LIU Haitao, CHENG Haifeng, CHENG Shaojun, TANG Gengping, ZHOU Yongjiang

2007, 27(6): 69-74.

[Abstract](1609) [PDF 1746KB](319)

Abstract:
A new type radar absorbing structure derived from Salisbury screen,which was named resistive capacitive FSS absorber,was presented.The absorbing properties of FSS absorbers were investigated with finite element method and the results showed that the sheet resistance of FSS unit cell,the parameter p,parameter a and the thickness of dielectric layer were all able to affect the absorbing properties.The numerical analysis indicated that better absorbing properties would be attained when the sheet resistance of the FSS unit cell was from 100Ω/□ to 200Ω/□ and the parameter p was about 0.05.The important law of "2h rule" was discovered.It was found that the functions of FSSs were not able to work very well if the total reflection points were too many within the frequency range of 2～18GHz,so the thickness of dielectric layer should not be beyond 5mm.The simulated results were validated by experiments,which were in good agreement.In addition,simulated and experimental results all indicated that the resistive capacitive FSS absorbers would realize strongly absorbing in lower frequencies but with fewer thicknesses if the proper parameters were chosen,and the absorbing properties of which would be excelled the traditional Salisbury screens.

Sliding Wear Resistance of Metal-PTFE Self-Lubricant Material

LI Weijing, CUI Shihai, HAN Jianmin

2007, 27(6): 75-78.

[Abstract](1522) [PDF 1067KB](331)

Abstract:
The wear resistances of ADI bush material and metal-PTFE self-lubricant bush material was comparatively investigated.It was found that the friction coefficient of friction couples consisting of metal-PTFE self-lubricant bush material and 45 steel was obviously lower that of friction couples consisting of ADI austempered ductile iron and 45 steel.And the wear resistance of metal-PTFE self-lubricant bush material was superior to that of ADI austempered ductile iron.The wear resistance of 45 steel coupled with metal-PTFE self-lubricant bush material was also better than that of 45 steel coupled with ADI austempered ductile iron because of the good self-lubricant property of metal-PTFE material.

Aging Mechanism of Polysulfide Sealant in Jet Fuel

WU Songhua, YI Xiaosu, QIN Pengbo, WANG Jinghe, GUO Meili

2007, 27(6): 79-82.

[Abstract](1195) [PDF 1034KB](306)

Abstract:
Polysulfide sealant is seriously aging in aeronautic jet fuel.The feature of aging proceeding of polysulfide sealant in jet fuel,chemical change of jet fuel in the high temperature air,and the effect of such change on polysulfide sealant were studied by the means of function detection,chemical analysis,and instrumental analysis.The factors and mechanism which induce seriously aging of polysulfide sealant in jet fuel were analyzed.The results shows that effect of both heat and oxygen leads strength and elasticity of polysulfide sealant to decrease greatly in jet fuel,and obvious weightlessness.The specific process was,at first,jet fuel was oxidized by oxygen in air,peroxide was greatly produced;then polysulfide sealant could be swellinged by hot jet fuel,its velocity of absorbing oxygen increased enormouslu,so degradation and cross-link interlaced to happen.

2007 Vol. 27, No. 6