航空材料学报

Effect of Surface Recrystallization on Microstructure and Mechanical Properties of Nickel Base Single-crystal Superalloy DD5

LI Zhi-qiang, HUANG Zhao-hui, TAN Yong-ning, ZHANG Qiang, ZHANG Hong-wei, JIA Xin-yun, WANG Yan-li

2011, 31(5): 1-5.

[Abstract](1546) [PDF 1798KB](244)

Abstract:
The evolution of recrystallized microstructure and the change of mechanical properties with different heat-treatment temperature and deformation were studied for the second generation single crystal superalloy DD5.The results showed that the recrystallization occurred in the grit blasted sample at heat-treatment temperatures higher than 1050℃.At the initial stage the recrystallization texture was characterized by cellular morphology of recrystallization,and then,with the increase of heat-treatment temperature,it was transformed into recrystallized layer.The recrystallization depth for grit blasted samples was thicker than water-grit blasted ones.It was found that the tensile property and stress-rupture property of the superalloy DD5 was decreased with the recrystallized layer,and the higher the heat-treatment temperature,the stronger the decreasing extent.

Effects of Zn Addition on Microstructure and Mechanical Properties of Mg-10Gd-4.8Y-0.6Zr Alloy

LI Hui-zhong, LIU Hong-ting, CHEN Jian-mei, WANG Hai-jun, LIANG Xiao-peng

2011, 31(5): 6-11.

[Abstract](1274) [PDF 2354KB](190)

Abstract:
Effects of Zn addition on the microstructure and mechanical properties of Mg-10Gd-4.8Y-0.6Zr(mass fraction/%,the same below)alloy during extrusion and following isothermal aging at 200℃ were investigated using digital micro-hardness testing,mechanical testing,optical microscopy(OM),scanning electron microscopy(SEM),transimission electron microscopy(TEM),X-ray diffraction(XRD).The results showed that Zn obviously refined grains of the alloy,and improved mechanical properties of the as-extruded alloys.In T5 condition the average grains of the alloy without Zn addition were about 25 μm;the average grains of the alloys with 1% Zn addition and 3% Zn addition were about 15 μm and 10 μm,respectively.For the alloy with 1% Zn addition in the-extruded and aged states,the values of tensile strength reached 337 MPa and 397 MPa,yield strength reached 128 MPa and 148 MPa,and the ductility rate reached 10.0% and 5.0% respectively,the better comprehensive properties were exhibited.

Effects of Zr Contents on Properties of Mg-Zr PM Damping Alloys

LIU Zi-li, SHEN Ping, ZHOU Gui-bin, LIU Xi-qin, LIU Bo-lu

2011, 31(5): 12-17.

[Abstract](1357) [PDF 1978KB](208)

Abstract:
Mg-x/% Zr damping alloys(x=0.6,1.5,2.5,5,mass fraction/% the same below)were prepared by PM(powder metallurgy)technology,and effects of Zr contents on microstructure,mechanical properties and damping capacities of Mg-x%Zr damping alloys were researched by three-point bending test and DMA,etc.The results show that the microstructure become into strip-shaped morphology,more granular particles appear in the grain boundaries or inside grains,and the grains are more refined with the increase of Zr additions.Relative density,micro-hardness and bending strength of the Mg-xZr damping alloys increase with increasing addition of Zr,and reach the maximum value with Zr addition of 2.5%.Under the testing conditions of 5 Hz frequency and 6×10-5 strain amplitude,Mg-5%Zr alloy exhibits the highest damping capacity with tan value reaches to 0.084,the Mg-1.5%Zr alloy is next,and Mg-2.5%Zr alloy has the worst damping capacity.The damping capacities of Mg-xZr alloys increase slowly with the temperature from 27℃ to 100℃,and increase rapidly above 100℃.The damping peaks appear at temperature of 160℃.The temperature of the damping peak of Mg-1.5%Zr alloy increases with increasing frequencies,showing the characteristic of relaxation damping.

Investigation on Artificial Aging and Creep Aging of 6156 Aluminum Alloy

JIN Kun, DENG Yun-lai, ZHOU Liang, WAN Li, ZHANG Xin-ming

2011, 31(5): 18-22.

[Abstract](1440) [PDF 1341KB](283)

Abstract:
The characteristics of strengthening and microstructure of 6156 Aluminum alloy under the conditions of artificial aging(AA)and creep aging(CA)were studied by the techniques of optical microscopy(OM),transmission electron microscopy(TEM),Vicker hardness test,tensile properties test and electric conductivity test.The results show that the peak mechanical properties of the samples treated by various AA or CA schemes have little difference within scales of temperature(155～175℃)-loading stress(0～200MPa)-time(8～14h).However,the amount of precipitates increased and the sizes of them decreased,and then both the mechanical property and electrical conductivity of the CA samples increased as compared with that of the AA samples.The primary creep strains accounted is more than 85% of the total amount strains,and increased extremely with the loading stresses increased.The peak mechanical properties of the CA samples were not sensitive to the testing temperatures and stresses,but the creep strains of them were sensitive to the loading stresses.This implies that the 6156 Aluminum alloy is suitable to creep age forming(CAF)of component.

Model Calculation of Heat Transfer Coefficient of Quenched Cooling under Jet Impingment Plate

DENG Yun-lai, HE You-wei, CAO Sheng-qiang, ZHANG Xin-ming

2011, 31(5): 23-28.

[Abstract](1377) [PDF 745KB](217)

Abstract:
The quenched cooling heat transfer process of the thick plate by multi-nozzle jet impinging is extremely complicated,thus it is difficult to establish a model of the surface heat transfer coefficient distribution,which reveals the speed of the heat transfer on the jet impinging surface.In this paper,the mathematical model of multi-nozzle jet simultaneously impinging quenched cooling has been established,coefficient distribution law at the stagnation and turbulent zone has been calculated by actual measurement of the cooling curve and has been verified based on the ABAQUS simulation software.The results show that the coefficient distribution at the stagnation and turbulent zone is uneven over time,and the peak appeared within 10 to 20 seconds,and then comes to the variation of the next waves.The actual measurement(or calculation)of the cooling curves at the sample's center and surface is at a very good match state with that of simulation,therefore it verifies the heat transfer coefficient distribution model under the multi-nozzle jet simultaneously impinging.

Study on Clad of Nickel Base Alloys Based on Rare Earth Added Clad Alloy

LI Yong-ping, XU Yi-wen, XU Pei-quan

2011, 31(5): 29-33.

[Abstract](1251) [PDF 1808KB](226)

Abstract:
On the basis,overlaying welding experiment was carried out and the macrostructure and microstructure distribution were analyzed.Consequently,the micro hardness distribution was detected.The results show that the proposed nickel base alloy consists of γ-(Ni,Fe),FeNi3,Ni and little Fe2C.The microstructure of clad distributed homogeneously without gas porosity and cracking.The micro hardness is increased from 174HV0.2 to 780HV0.2.

Influence of Grain Size on Microstructure and Mechanical Properties of Ti Alloy in TIG

ZHOU Shui-liang, TAO Jun, ZHAO Hai-tao, GUO De-lun

2011, 31(5): 34-39.

[Abstract](1357) [PDF 2306KB](231)

Abstract:
Fine grain TC4 alloy with various grain size(2μm,8μm,19μm)were welded by conventional TIG respectively,the microstructure and mechanical properties of welded joint were tested.The results show that the microstructure of weld center(WC)and heat-affected zone(HAZ)are α martensites.With the same parameters,and the reduction of grain size of base metal(BM),the microstructure of WC and HAZ change from lamellar α structures to basket α structures.With the reduction of grain size of BM,the grain growth tendency of HAZ become more apparent,the width of FHAZ is reduced,and the width of CHAZ is increased obviously,the crystal grain gradient of WC-HAZ-BM is increased,the grain transition of these three zones got worse,and the tensile strength and elongation were increased slightly.Tensile fractures of welded joint present character of quai-cleavage crack.Cleavage features of fractographs of weld joint are more obvious with increasing grain size of the base metal.

Effects of Microstructures of Micro-arc Oxidation Films from TC4 Alloy on Adhesion Property of Electroless Ni-P Platings

FENG Chang-jie, WANG Qi, ZHOU Ya, ZHAO Qing, DU Nan

2011, 31(5): 40-46.

[Abstract](1375) [PDF 2449KB](234)

Abstract:
Electroless Ni-P platings were deposited on Micro-arc Oxidation(MAO)films from TC4 alloy prepared for different time.The influence of different microstructures of the MAO films on the adhesion property between the electroless Ni-P plating and the MAO films were investigated by SEM,automatic scratch tester and thermal shock tests.The results show that with the increase of MAO time,the roughness and the radius of the microholes on the surfaces of the MAO films increases correspondly.In addition,the shape of the microholes grows open,and then closes slowly,and finally becomes a groove.With the time of MAO increasing from 3min to 15min,the adhesion property between electroless Ni-P platings and MAO films degrades,and the critical load decreases from 21.5N to 8.5N.Besides,the typical feature of the scratch changes from cracks to flakes.Further increasing the MAO time from 15min to 60min,the adhesion property between Ni-P electroless platings and MAO films becomes better obviously,and the critical load increases from 8.5N to more than 40N.It can be seen from the thermal shock tests that after the first thermal cycle,serious peelings of Ni-P electroless plating occur,and the sequence of beginning peeling of the Ni-P electroless plating from different MAO films is MAO for 15min,7min and 3min.Peelings appear from MAO for 30min after 2 thermal cycles,and for MAO of 60min is 28 thermal cycles.The results from the thermal shock tests are consistent with those of the scratch tests.In addition,the models of the microstructures of the MAO films processed for different time is built,and the adhesion property between the microstructures of the MAO films and the Ni-P electroless platings is discussed as well.

Effect of Growth Technology of TiO₂ Film on Photoelectronic Properties of TiO₂ UV Detector

QI Hong-fei, LIU Da-bo

2011, 31(5): 47-50.

[Abstract](1370) [PDF 422KB](248)

Abstract:
Different TiO2 films with the same thickness were prepared by RF magnetron sputtering and Sol-Gel respectively.Then,MSM-type TiO2 UV detectors were made with the TiO2 films.The effect of growth technology of TiO2 film on photoelectronic properties was investigated through SEM,XRD,and the detection of photoelectronic properties.It was found that those UV detectors with TiO2 layer prepared by magnetron sputtering had high sensitivity and fast time responses.In this case,the TiO2 that film possesses high quality and high sheet resistance is considered as the film with the excellent photoelectronic properties for TiO2 UV detector.

Tribological Properties and Wear Mechanisms of the Couple of 3D Needled C/SiC Composite and 30CrSiMoVA

LIU He-yi, FAN Shang-wu, YIN Xiao-wei, YUAN Qi, ZHANG Li-tong, CHENG Lai-fei

2011, 31(5): 51-57.

[Abstract](1345) [PDF 2151KB](212)

Abstract:
The tribological properties of the couple of three-dimensional needled C/SiC composite and 30CrSiMoVA were investigated on MM-1000 Ⅱ friction testing machine.The wear mechanisms and phase transformation were analysed with SEM,XRD,EDS,thermodynamics,and finite element simulation of braking temperature field.The results show that,with the increase of the initial braking speed,the average friction coefficient of the couple of three-dimensional needled C/SiC composite and 30CrSiMoVA decreases,the temperature of friction surface increases,and the linear wear rate of three-dimensional needled C/SiC composite and 30CrSiMoVA tended to increase.When the initial braking speed is greater than 15m/s,the maximum temperature on the friction surface exceeds 560 ℃.Besides,Fe3C,Fe3Si,FeO,γ-Fe2O3and α-Fe2O3 was found,which was supposed come from the reactions of Fe,SiC,Si and O2.This reaction together with abrasive wear adhesive wear and fatigue wear,accelerate the wear of materials.

Study on Property and Structure of Duplex Lubricating Film with Lower Friction Coefficient

YAN Lai-cheng, TAN Hua-yu, HAN Huan-qing, LUO Xi-yu

2011, 31(5): 58-61.

[Abstract](1347) [PDF 1124KB](212)

Abstract:
Duplex lubricating films with lower friction coefficient were prepared on aluminum alloy by micro arc oxidation(MAO)and spraying MoS2-based lubricant material which was solidified about two hours at 150～200℃.The effect of structure and properties on the friction coefficients were studied.The results illustrate that the compact zone mainly containing γ-Al2O3 was obtained by removing the surface loose zone of MAO film,its surface hardness was improved obviously and the friction coefficient of duplex lubricating film was decreased significantly.The surface hardness of compact zone and loading were main factors to the friction coefficients which were in the range of 0.05～0.08 steadily,and the processing of duplex lubricating film has a little effect to tensile properties of the base aluminum alloy.

Effect of Sintering Temperature on Ceramic Cores Performances of SiO₂-ZrO₂ system

LIU Xiao-guang, QI Chang-jian, HE Li-li, TANG Ding-zhong, XIAO Cheng-bo, YAO Jian-sheng, GU Guo-hong, LI Xin

2011, 31(5): 62-65.

[Abstract](1416) [PDF 1134KB](288)

Abstract:
The easy leachable SiO2-ZrO2 ceramic cores used in directional solidification and single crystal hollow blades were prepared by traditional hot-pressure casting.The results show that the a sintering shrinkage increased with the increasing sintering temperature from 1150℃ to 1250℃,and sintering shrinkage is increased markedly above 1200℃.Well-grown crystalline grains were shown,and main compositions are composed with non-crystal silica,cristobalite and zirconia.The material properties sintering at 1200℃ are optimized,and bending strengths reach 42.9MPa,and best anti-deformation and bending strengths are also obtained at 1550℃.High temperature anti-deformation is 0.1mm,and the high temperature bending strength,pore,densiy and sintering shrinkage are 27.9MPa,30.4%,1.92g/cm3 and 0.4% respectively.The formations of cristobalite is about 20%.It meets the pouring requirement for superallay hollow turbine blades of the aero-engine.

Effect of Heat-resistant Additive on Flammability of Silicone Rubber

LAI Liang-qing, SU Zheng-tao, QIAN Huang-hai, WANG Jing-he

2011, 31(5): 66-70.

[Abstract](1286) [PDF 1099KB](219)

Abstract:
The effect of heat-resistant additive on flammability of silicone rubber was investigated by analysis method such as Oxygen Index,TGA-DSC and SEM.It is found that the heat-resistant additives Fe2O3,CeO2 and TiO2 improve the hot air ageing properties and flame-resistance of silicone rubber,but the effect of 300℃ hot air on flammability of silicone rubber is indistinct.Heat-resistant additive inhibits oxidized breakage of the pendant group of silicone rubber,and the initial decomposition temperature is increased more than 30℃,and the decomposition release heat is decreased about 62%.The SEM of combustion results show that through the mechanism of eliminating free-radical,heat-resistant additive can inhibit oxygen from attacking to the pendant group,thereby reducing the decomposition of silicone rubber obviously and improving the flammability of silicone rubber.

Creep Behavior and Fracture Mechanism of HCR GH4169 Superalloy

LI Zhen-rong, TIAN Su-gui, ZHAO Zhong-gang, CHEN Li-qing, LIU Xiang-hua

2011, 31(5): 71-76.

[Abstract](1377) [PDF 1388KB](198)

Abstract:
By means of the creep curves measurement and microstructure observation,the creep behavior and fracture mechanism of HCR + DA GH4169 nickel-base superalloy are investigated.Results show that microstructure of HCR GH4169 alloy consists of the γ',γ" phase and γ matrix,and possessing in the fine grains in which exists significant amount of dislocations and twinning.After direct aged treated.the quantities of the dispersed fine γ" phase increases and the alloy retains the effect of the deformed strenghtening during hot continuous rolling,which is thought to be the main cause of the alloy possessing a longer creep lifetime under the applied stress of 725 MPa at 650℃.During creep,the deformation features of the alloy are twining and double orientation slipping of the dislocations.As the creep goes on,significant amount of dislocations is plied up the regions near the boundaries to bring out the stress concentration,which results in the initiation and propagation of the micro-cracks along the boundaries up to rupture.

Crack Growth Characteristic for Diffusion Bonded Laminates of TC4 Titanium Alloy with Localized No-Welded Area

HE Xiao-fan, LIU Yan-mao, LIU Wen-ting, SUN Yan-peng, WANG Xiang-ming

2011, 31(5): 77-81.

[Abstract](1431) [PDF 1218KB](190)

Abstract:
To research the crack growth characteristics of diffusion bonded laminates with localized no-welded region of TC4 titanium alloy,the fatigue tests for 8mm thick TC4 three-layer diffusion bonded laminates with localized φ12mm and φ15mm no-welded area were conducted under the constant amplitude fatigue stress of R=0.093 inserted with marker load of R=0.7.The crack growth(a,N)data were obtained by QF.The analysis on the failure surface shows the crack growth could be divided into three phases.The contrast on the da/dN-a curves of those coupons shows that the crack growth characteristic in the no-welded area has no difference,the crack growth rate of the φ15mm no-welded area is lower than that of φ12mm no-welded area in the welded boundary area.

Investigation on Fatigue Crack Propagation Behavior of TC11 and TC4 Ti Alloys at Room Temperature and 400℃

HUANG Xin-yue, ZHANG Shi-chao, LU Yuan, YU Hui-chen

2011, 31(5): 82-85.

[Abstract](1403) [PDF 1084KB](242)

Abstract:
The fatigue crack propagation behaviors of two brands titanium alloys,TC11 and TC4,are studied.Fatigue crack propagation rate tests at room temperature and 400℃ were carried out.Results of the tests indicate that the experimental data at 400℃ seems more scatter than data at room temperature for both Ti alloys,especially for TC11.The reason of data scatter is discussed.Because of the high data scatter,the linear regression based on the average expectation is no longer suitable.Thus the prediction is non-conservative because of the large deviation of crack propagation rates on the high rate side.A new data fitting policy based on high propagation rate points is proposed.It is found that at room temperature and 400℃,the crack propagation rate of TC11 is slower than TC4.Consequently TC11 is better than TC4 from the damage tolerance point of view.

Fatigue Life Evaluation on Plane Structural Parts with Holes through Local Strain Method

TONG Di-hua, CHEN Zhi-wei

2011, 31(5): 86-90.

[Abstract](1242) [PDF 1345KB](246)

Abstract:
The thesis introduces the work of calculating local stress and local strain by application of Levenberg-Marquardt's iteration method.As an usual mathematical method to solve super equation,Levenberg-Marquardt's iteration method has some disadvantages such as complicated program,low computing efficiency.Therefore,the paper aims to find out a comparatively simple,high efficient and high precision computing method.Through comparing and analyzing the efficiency and precision of dichotomy and Levenberg-Marquardt's iteration method by which solving strain life equation and local strain range,the thesis proves that the application of dichotomy is simple and applicable for the engineering.At last,through combination with the case of plane's drilled component,applying local stress strain method to calculate the parts' predictive life and comparing that result with the experimental life value,the paper concludes that strain life equation which concerns mean stress correction more fit for engineering requests.

New Assessment Method of Initial Fatigue Quality and Crack Growth Rate

YANG Mou-cun, NIE Hong

2011, 31(5): 91-94.

[Abstract](1681) [PDF 817KB](191)

Abstract:
How to assess initial fatigue quality and crack growth rate rapidly and economically is the key of durability investigation.At present,experimentation is used to assess durability,which is very costly and time-consuming.Performance degradation curve includes a lot of information about fatigue failure.Based on the tests for specimens with one rivet hole respectirely,a new method of determining initial fatigue quality and crack growth rate with performance degradation curves of specimens are presented in the paper.According to the test results and theoretical derivation,the relationship of crack length with loading cycle is established.Then,the equivalent initial flaw size(EIFS)values are calculated and fatigue crack growth rates are estimated by using exponential fitting technique.The applicability and validity of the method are verified with theoretical computation of fracture limit finally.

2011 Vol. 31, No. 5