航空材料学报

Microstructure and Mechanical Properties of Mg-4.9Zn-0.9Y-0.7Zr Alloy

WANG Bin, YI Danqing, LUO Wenhai, FANG Xiya, LIU Huiqun, WU Chunping

2009, 29(2): 1-7.

[Abstract](1502) [PDF 2354KB](257)

Abstract:
Mg-4.9Zn-0.9Y-0.7Zr alloy and Mg-4.9Zn-0.7Zr alloy were prepared by ingot metallurgy method.The influence of Y addition on microstructure and properties was studied.Phase analysis,microstructure and morphology of second phases were investigated by XRD,OM and SEM.The component and morphology of the second phases was analyzed by EDAX and TEM.The results showed that Y was an effective element strengthening Mg-Zn-Zr alloy and a large number of Mg3Zn6Y phase formed due to the addition of Y.During the process of hot rolling,Mg3Zn6Y phase was pulverized into large amount of dispersion particles,which pinned dislocation effectively,so ultimate strength and yield strength at room temperature were improved,as well as good plasticity was remained.

Corrosion Study of Pure Aluminum in 0.6mol/L NaCl Solution by SECM

ZHOU Herong, MA Jian, LI Xiaogang, DONG Chaofang, LU Qikai, FENG Hao

2009, 29(2): 8-12.

[Abstract](1479) [PDF 1237KB](521)

Abstract:
The corrosion behavior of aluminum alloy 1060 in 0.6mol/LNaCl(5 mmol/L KI) solution was investigated by scanning electrochemical microscopy(SECM).The surface morphology was observed by scanning electron microscope(SEM).The corrosion products were analyzed by energy dispersive X-ray detector(EDX).The result showed that the dissolution of aluminum alloy 1060 was different in different region of the surface.The distribution of the oxidation current peak on the surface of the sample was strip in form.The dissolution position mainly happened in the round of FeAlx.The corrosion products were not uniform and the amount was little.The corrosion spot was mainly round.

Effect on Precipitation Phases of 7B04 Aluminum Alloy during Creep Process

LI Chao, WAN Min, HUANG Lin

2009, 29(2): 13-17.

[Abstract](1521) [PDF 1158KB](369)

Abstract:
Based on several age creep experiments in different temperature,the suitable creep temperature was 150℃.And TEM results show that high stress can accelerate the transformation of precipitation,as well as increase the flowability of dislocations.Thus,during the early stage of creep at 150℃,the yield stress value was dramatically increased and achieved the maximum,then decreased with the increase of the creep time.

Study on Microstructure and Mechanical Properties of Roll Forming Profiled Stainless Steel Wires Used for Metal Rubber

NIU Li, DONG Xiuping, YANG Jianchun, LIU Guoquan, BAI Hongbai

2009, 29(2): 18-24.

[Abstract](1514) [PDF 2089KB](177)

Abstract:
The microstructure and mechanical properties of profiled stainless steel wires used for metal rubber components were studied by means of optical microscopy,three-dimensional imaging system,SEM,X-ray diffraction and FEM.The wires were rolled down under a series of different rolling speeds in cold rolling and between 410~1270℃ in hot rolling.The deformation-induced martensite content in the 0.4mm cold-drawn stainless steel wires was 82.1%,the martensite content in the profiled stainless steel wires increased in cold roll forming and decreased incoordinately in hot rolling.SEM observations showed that there were large quantities of voids in the profiled stainless steel wires,but the voids were less than which in the cold-drawn stainless steel wires.On the condition of definitive rolling speed,the volume fractions of voids increased with the temperature build-up.Compare with the cold-drawn stainless steel wires,the tensile strengths of the cold roll forming wires were 1374~1553MPa,the hardness were 402~510HV.On the condition of definitive rolling speed,the tensile strengths and hardness of the wires decreased with the temperature build-up,and the elongation increased.The deformation arearatio of roll forming profiled stainless steel wires is 49.8%.

Effect of Equal Channel Angle Pressing(ECAP) Technology on Microhardness of Ti-1023 Alloy

YUAN Shichong, GUO Hongzhen, ZHAO Zhanglong, WANG Tao, YAO Zekun

2009, 29(2): 25-28.

[Abstract](1518) [PDF 1572KB](314)

Abstract:
The microhardness of Ti-1023 alloy processed by ECAP technology elevated firstly and then decreased with the sustain raise of extrusion temperature and the peak value appeared when pressed in 780℃.This change of microhardness related with composition of primary αphases,secondary αphases and β phases in microstructure.The hardness of samples after annealing was lower than samples without annealing as the extrusion temperature under the β-transus(Air cool).As extrusion temperature surpassed the β-transus(Water cool),the hardness of samples after annealing increased remarkably due to the metastable β phases and the decomposition of martensite by cooling in water after pressing which made refined flake α phases precipitated during annealing.The standard heat treatment increased the hardness of the pressing samples.And samples pressed surpassed the β-transus gained better reinforcement after the standard heat treatment.

Effect of Predeformation on Microstructures and Mechanical Properties of Al-Cu-Mn-Mg-Ag Aluminum Alloy

LI Huizhong, LI Zhou, LIANG Xiaopeng, GUO Feifei, SUN Fengwei

2009, 29(2): 29-33.

[Abstract](1428) [PDF 1517KB](252)

Abstract:
The effect of predeformation on the microstructures and mechanical properties of Al-Cu-Mn-Mg-Ag aluminum alloy were investigated by means of microhardness test,tensile test,scanning electron microscopy(SEM) and transmission electron microscopy(TEM).The results show that the cold roll deformation of Al-Cu-Mn-Mg-Ag aluminum alloy accelerates the ageing process,increases the peak hardness,promotes the phase precipitation and increases the number of phase.The double-stage hardening character is weak with increasing predeformation amount during the ageing process.When the amount of predeformation is less than 10%,there is apparent double-stage hardening character.However simple hardening character appears as the amount of predeformation higher than 10%.The tensile strength and yield strength of alloy are gradually increased,but the plasticity is decreased with increasing pre-deformation amount.The predeformation of 10%～20% for Al-Cu-Mn-Mg-Ag aluminum alloy is better according its strength and plasticity.

Study on Modified Heat Treatment for DD3 Single Crystal Superalloys

HAN Mei, LUO Yushi

2009, 29(2): 34-38.

[Abstract](1536) [PDF 519KB](182)

Abstract:
To fully evaluate the feasibility of improving the heat treatment for DD3 single crystal,the effects of a modified heat treatment on microstructure and properties were investigated.Experimental observation was gained through metallography,differential thermal analysis,physicochemical phase analysis and creep testing.Experimental results show that the modified heat treatment increases the γ′size and improves the range of γ′size distribution,also increases the γ′mass fractions,especially the mass fractions of larger γ′,which contribute to improvement of creep properties at 760~1038℃.

Microstructure of Ceramic Coating on Ti6Al4V Alloy by Microarc Oxidation Technology

MENG Xiaojuan, LI Weijing, CUI Shihai, HAN Jianmin

2009, 29(2): 39-42.

[Abstract](1507) [PDF 900KB](323)

Abstract:
A dense ceramic coating with 100 micron was successfully produced on Ti6Al4V alloy by using microarc oxidation method in order to improve its wear resistance.SEM results showed that the ceramic coating was well bonded with the substrate.XRD showed that the ceramic coating was mainly composed of Al2TiO5 and Rutile.The microhardness test showed that the microhardness of ceramic coating was 862HV while that of the substrate was only 412HV.The microhardness of the ceramic coating was obviously higher that of the substrate,which means that the ceramic coating produced by microarc oxidation method can improve the wear resistance of titanium alloy.

Preparation and Fretting Wear Performance of Microarc Oxidation Coating on TC4 Titanium Alloy

LIN Xiuzhou, ZHENG Jianfeng, LIN Zhijun, ZHU Minhao

2009, 29(2): 43-47.

[Abstract](1497) [PDF 1216KB](316)

Abstract:
Micro-arc oxidation(MAO) coating was prepared on TC4 titanium alloy surface using own made micro-arc oxidation device.Characterizations of the MAO coating were carried out by several surface analysis method which included Vickers hardness,profilometer,SEM,EDX,XRD et al.Performances of fretting wear of the coating against GCr15 steel ball were tested on a DeltaLab NENE-2 fretting wear tester.The results indicated that the MAO coating with rough surface,high hardness and typical porous ceramic structure was mainly consist of rutile TiO2,anatase TiO2 and a little Al2O3 phases.After micro-arc oxidation,the anti-wear performance of fretting wear for the substrate alloy has been improved greatly.In the partial slip regime,the friction coefficients of the coating increased with the increase of the displacement amplitudes.And in the mixed and slip regime,the friction coefficients in steady-state stage of the coating were independent upon the displacement amplitudes.In the partial slip regime,the damage of the coating was very slight.The fretting wear mechanisms of the MAO coating in the mixed and slip regime were mainly abrasive wear,oxidation wear and delamination.

Effects of Addition of Nanosize Alumina on Microstructure and Properties of Zirconia Coatings

LIANG Bo, DING Chuanxian

2009, 29(2): 48-52.

[Abstract](1384) [PDF 1769KB](263)

Abstract:
Three ZrO2 coatings with different Al2O3 contents were deposited by air plasma spraying using nanosize Al2O3 and ZrO2 powders as raw materials.The characterizations of zirconia-alumina composite coatings were studied by FESEM,SEM,TEM,XRD and Raman spectroscopy,and the properties such as cohesion strength,microhardness were also detected.The results show that the deposition efficiency,cohesion strength and microhardness can be considerably increased due to the addition of nanosize alumina,which are benefit to improvement of the anti-wear properties of zirconia coating.The bimode structure and rich-alumina splat are observed in zirconia coating,and the alumina grain is noncrystlline.The peaks of zirconia observed in Raman spectroscopy and XRD patterns of the zirconia/alumina composite coatings become broaden due to the addition of alumina.

Methods of Studying Welds Shape of TC4 Alloy with EBW

WANG Yajun, FU Pengfei, GUAN Yongjun

2009, 29(2): 53-56.

[Abstract](1520) [PDF 560KB](329)

Abstract:
Many methods of studying typical character of electron beam welding(EBW) welds shape had been introduced,including experiments,theoretic analytics,numerical simulation,Regression analysis and artificial neural network.The results showed it was reasonable scheme,which combined several methods to study welds shape.There were a lot of key points gained from weld figure,and parameterize recurrence were achieved by B-spline curves to connect these points.The relationship between parameter for key point and that for weld shape were analyzed.The classifying criterion for EBW welds shape was build and the critical value for key dimension was obtained.Welds shape with EBW were classified as Funnel pattern,Bell pattern,Chock pattern and Nail pattern.

Influence of Welding Processes on Mechanical Properties of Aluminum Alloy 2219

PENG Xingna, QU Wenqing, ZHANG Guohua

2009, 29(2): 57-60.

[Abstract](1551) [PDF 1337KB](445)

Abstract:
Both types of welds,friction stir welds of aluminum alloy 2219 and variable polarity gas tungsten arc welds of the same alloy were made and mechanical properties were evaluated by tensile testing.It is shown that the FSW welds had better performances than VPTIG welds,although both welding processes decreased the mechanical properties of aluminum alloy 2219 base metal plates.The weld metals and base metals were characterized by scanning electron microscopy and optical microscopy.According to fractography and microstructures analysis,the weld nugget zone(WN),where the dynamic recrystallization occurred,consisted of refined and equiaxed grains structure and FSW tensile specimens fractured at the retreating side.Variable polarity TIG specimens are liable to produce defects such as a high concentration of gas porosity and fusion zone is the weakness.

Simulation and Modeling of Polymeric Composite Temperature Change during Manufactory Process

CHEN Xiangbao, XING Liying, ZHOU Zhenggang

2009, 29(2): 61-65.

[Abstract](1399) [PDF 1224KB](517)

Abstract:
Based on polymeric composite matrix curing dynamic equation,the curing reaction heat was introduced in the heat conductive equation via heat reaction dynamics.Temperature distribution models for polymeric material curing process were established by simulating the actual manufactory conditions.Compared between calculated values and actual values,it is found that the temperature distribution simulation technique for manufactory process can exactly predict epoxy and BMI polymeric composites temperature changes during manufactory.

Modified Bismaleimide(BMI) Resin and Its Application in RFI

CAO Wei, CHEN Lixin, LIANG Bin, DONG Jianna, SONG Jiale

2009, 29(2): 66-70.

[Abstract](1396) [PDF 1553KB](240)

Abstract:
5405A resin film,which the requirements of resin film infusion(RFI) process,was developed by adding PES into 5405 modified bismaleimide resin.It can be flexible arbitrarily and shows no stickiness at room temperature.The time of keeping lower viscosity(viscosity≤500mPas) was 44 min at the infusing temperature(130℃).The insoluble matter content of resin changed from 1.25% to 2.02%,there was no obvious difference for initial temperature and peak temperature on DSC curves and the gel times were 137min and 135min respectively at 130℃ before and after storing for 3 months at ambient temperature.The net resin and untwisted plain weave G0827 carbon fabric reinforced 5405A composite laminates were fabricated.Comparing with 5405 resin,flexible and tensile property of solidified 5405A decreased,but toughness increased.

Approximate Calculation of Stress Distribution Near Hole for Composite Laminates with Finite Width

ZHU Xiping, GUO Zhangxin, HAN Xiaoping, ZHI Xizhe

2009, 29(2): 71-75.

[Abstract](1447) [PDF 262KB](460)

Abstract:
Theoretical calculation method for stress concentrations in anisotropic plates with a circular hole was applied to composite laminates with a circular hole.Based on the classical laminated plate theory,a finite composite laminate with a circular hole was treated as an anisotropic plate.Then the anisotropic plate equivalently was transformed into a unidirectional composite laminate subjected to off-axial loading.Finally stress concentration factor of composite laminates with a circular hole was obtained by means of a similar calculation formulas in unidirectional composite laminate subjected to off-axial loading.According to the derived expression,effects of the related parameters,such as d/W(hole diameter-plate width) ratio,fiber layups,constant of material property on stress concentration were analysed.

Analysis of Deformation and Stress of PMMA Hollow Transparency Used in Porthole

LIU Lizhong, JI Yipu, BAO Yiwang, ZUO Yan

2009, 29(2): 76-80.

[Abstract](1466) [PDF 635KB](224)

Abstract:
The iterative algorithm and finite element model were built to investigate the deformation and stress of PMMA hollow transparency used in porthole according to the specific loading characteristics.The deformation obtained from proof tests and calculations were consistent with each other,which implied the accuracy of the algorithm and finite element model.Then the calculations were performed to deal with different pressure out of cabin,different thickness of PMMA panel,and different thickness of gas layer.The relations of deformation(or stress) and pressure out of cabin,thickness of PMMA panel,thickness of gas layer were obtained and analyzed.

Effect of Different Ways of Heating and Loading on Stress Distribution of Cylinder Model with Prestrained NiTi Fiber

HE Weibo, JIN Ming, ZHAO Yongli

2009, 29(2): 81-84.

[Abstract](1588) [PDF 365KB](165)

Abstract:
A typical cylinder model with a prestrained NiTi fiber was employed to analyse the stress transfer.During the reverse transformation and under the simplified conditions,the stress formulae of the NiTi fiber and the interface were obtained.Additionally,the effective austenite start temperature of the NiTi fiber was determined according to its axial stress.It is shown that there are different stress distributions for different ways of heating and loading,due to the effect of NiTi fiber axial stress on the effective austenite start temperature.Upon loading then heating,the effective austenite start temperature of the NiTi fiber is higher,and the process of the reverse transformation is shorter,so the NiTi fiber axial stress and the interface shear stress become lower.

Effect of Microdefects on Tensile Properties of High Volume Fraction SiC_p/Al Composites

KANG Xinmeng, CHENG Xiaoquan, LI Zhengneng, ZHANG Jikui, CUI Yan

2009, 29(2): 85-91.

[Abstract](1340) [PDF 1246KB](145)

Abstract:
The finite element models of high volume fraction SiCP/Al composites with microdefects were established.And the tensile mechanical properties of these composites were calculated.Through numerical simulation of typical microdefects as voids and interface debondings,it was found that the voids have a little effect on the tensile properties of this material.While interface debondings have the greatest effect on carrying load capability of the composites.Areas of debonded interfaces are inverse proportion to carrying load abilities of SiCP/Al composites.Different relative position between microdefects have different effect on tensile mechanical properties.Interfaces debonding near the void degrade carrying load abilities more than interfaces debonding far from the void.From the analysis of multi particulates models,it was found that the nonlinear stress-strain curve of high volume fraction SiCP/Al composites was correlated with gradual particulate interfaces debonding.Debonding proportion increase rapidly at the initial loading stage,and increase slowly near the breakage.

Study on Zirconium Metallic Coating for C_f/SiC Composites by Molten Salt Reaction

LIANG Chiyong, DU Yongguo, ZHANG Weijun, ZHENG Xiaohui, LU Yufeng, ZHOU Wenyuan

2009, 29(2): 92-96.

[Abstract](1384) [PDF 589KB](254)

Abstract:
Zirconium metallic coating was prepared on carbon fibre reinforced silicon carbide(Cf/SiC) composites by molten salt reaction method.The effects of reaction time on the morphology,phase composition and thickness of the metallic coatings on Cf/SiC composites were characterized by SEM and XRD.The interface reaction mechanism between SiC and Zr was investigated.The results show that the metallic coating is firstly deposited on the surface of SiC areas.With the increase of reaction time,the coating begins to deposit on carbon fibres.And,the surface of composites is covered by the metallic coating entirely when the reaction time is up to 3h.The main composition of coating is Zr,Zr3O,ZrC and Zr2Si.The control step for the formation of metallic coating is the diffusion of Zr,Si and C.

Fatigue Life Prediction for Center-Hole Specimen of 2024-T3 Aluminum Alloy Sheet Based on Small Crack Method

CHEN Bo, LIU Jianzhong, HU Benrun

2009, 29(2): 97-100.

[Abstract](1568) [PDF 1077KB](271)

Abstract:
Experimental and analytical studies were made on fatigue behavior and life prediction for center-hole specimen of 2024-T3 aluminum alloy sheet.The crack growth a-N data,which naturally initiated from notches under block spectrum,were achieved by the methods of fatigue striations and microscope observation.SEM observation was also made to get the initial flaw shape.A small crack methodology based on the plasticity-induced crack-closure concept and the corresponding analysis program FASTRAN3.9 was used to deduce the equivalent initial flaw size(EIFS) distribution from the test a-N data.Base on EIFS distribution and FASTRAN 3.9 program,the medium S-N curve was predicted and the result agreed well with the experimental data.

Transverse Tensile Properties and Fracture Behaviour of DD6 Single Crystal Superalloy

SHI Zhenxue, LI Jiarong, LIU Shizhong, ZHAO Jinqian

2009, 29(2): 101-104.

[Abstract](1596) [PDF 1268KB](313)

Abstract:
The transverse specimens of DD6 single crystal superalloy were prepared with seed method.The transverse tensile properties and fracture behaviour of single crystal superalloy DD6 at 760℃,850℃ and 980℃ were investigated.The transverse tensile properties were correspond with orientation longitudinal tensile properties.It indicates that the alloy exhibits excellent transverse tensile properties.The fracture mechanism of the transverse tensile of DD6 alloy at 760℃ and 850℃ showed qusi-cleavage,while the fracture mechanism at 980℃ showed dimple model.

2009 Vol. 29, No. 2