航空材料学报

2017-02-Catalog

2017, 37(2): .

[Abstract](1356) [PDF 873KB](6)

Abstract:

Grain Evolution in Process of Multi-pass Hot Deformation and Solution Heat Treatment of Al-Zn-Mg-Cu Aluminum Alloy

Yunqiang FAN, Shuhui HUANG, Zhihui LI, Xiwu LI, Yong'an ZHANG, Baiqing XIONG, Jianxin XIE

2017, 37(2): 1-6.

[Abstract](3238) [FullText HTML] (1348) [PDF 8657KB](17)

Abstract:
The grain evolution of Al-Zn-Mg-Cu aluminum alloy was quantitatively investigated during multi-pass hot deformation and solution heat treatment. The Gleeble 1500D machine was used to carry out the hot compression experiments. The effects of deformation, number of pass, temperature and strain rate on the average grain size, volume fraction of recrystallization and grain boundaries were characterized by electron back-scattering diffraction (EBSD). The results show that the average grain size, the volume fraction of small-angle grain boundary and recrystallization decrease with the decrease of number of pass; the volume fraction of high-angle grain boundary increases, and small-angle grain boundary decreases with the increase of deformation temperature; and the average grain size and the volume fraction of high angle grain boundary decrease with the increase of deformation; while an opposite tendency is shown in the change of the ratio of small-angle grain boundary.

Flow Stress Behavior of 15%SiC_P/8009 Aluminum Matrix Composite During Hot Compression Deformation

Yu WANG, Jie TENG, Shuang CHEN, Haibo LUO, Liulian TANG, Hui ZHANG

2017, 37(2): 7-12.

[Abstract](3766) [FullText HTML] (1390) [PDF 3336KB](17)

Abstract:
The flow stress behavior of 15%SiC_P/8009 aluminum matrix composite at deformation temperature of 400-550 ℃ and strain rate of 0.001-1 s^-1 was studied by hot compression testing on the Gleeble-3500 thermal-mechanical simulator. The results show that the flow stress increases initially and reaches a plateau after peak stress value with the increase of strain. The peak stress increases with the increase of strain rate and deformation temperature. The flow stress behavior can be described by the hyperbolic sine constitutive equation with the deformation activation energy Q of 488.3853 kJ/mol and the stress index n of 7.19022.

Preparation and Corrosion Resistance of Pulse-Current Anodic Oxidation Films of 2198 and 5A90 Al-Li Alloys

Peng YAN, Xinming LI, Linbo HE, Tailang XU, Haoran JU, Yanyu SONG, He'nan WANG

2017, 37(2): 13-20.

[Abstract](2580) [FullText HTML] (1273) [PDF 4677KB](9)

Abstract:
Anodic oxidation processes of 2198 and 5A90 Al-Li alloys were carried out with pulse-current (PC) in the mixture of acid solution of 18%(mass fraction, the same below) H₂SO₄+5%C₂H₂O₄ at room temperature. Surface and cross-sectional morphologies and composition distributions of anodic oxidation films were observed and determined by scanning electron microscope equipped with energy disperse spectroscopy (SEM/EDS). The corrosion resistances of these films were assessed by means of 10%NaOH aqueous solution dropping test and potentiodynamic polarization plot in 3.5% NaCl solution. The results show that the oxidation films of 2198 and 5A90 Al-Li alloys are mainly composed of Al oxides. For 2198 Al-Li alloy, fine and small particles evenly distribute in the oxidation film; and the film thickness is about 150 μm. For 5A90 Al-Li alloy, micro-pores existing in the film can provide better structure for later sealing; and the film thickness is nearly 180 μm. The larger thickness oxidation films of both two kinds of alloys prepared by pulse current anodic oxidation treatment have superior corrosion resistance in 3.5%NaCl solution.

Algorithm of Defect Segmentation for AFP Based on Prepregs

Zhiqiang CAI, Jun XIAO, Liwei WEN, Dongli WANG, Yaoping WU

2017, 37(2): 21-27.

[Abstract](2870) [FullText HTML] (1244) [PDF 2637KB](12)

Abstract:
In order to ensure the performance of the automated fiber placement forming parts, according to the homogeneity of the image of the prepreg surface along the fiber direction, a defect segmentation algorithm which was the combination of gray compensation and substraction algorithm based on image processing technology was proposed. The gray compensation matrix of image was used to compensate the gray image, and the maximum error point of the image matrix was eliminated according to the characteristics that the gray error obeys the normal distribution. The standard image was established, using the allowed deviation coefficient K as a criterion for substraction segmentation. Experiments show that the algorithm has good effect, fast speed in segmenting two kinds of typical laying defect of bubbles or foreign objects, and provides a good theoretical basis to realize automatic laying defect online monitoring.

Experimental and Numeral Investigation on X-cor Sandwich Structure under Low-velocity Impact

Fei ZHU, Dajun HUAN, Jun XIAO, Yong LI

2017, 37(2): 28-37.

[Abstract](3224) [FullText HTML] (1189) [PDF 8656KB](16)

Abstract:
X-cor sandwich is a new kind of foam sandwich reinforced by Z-pin techniques. Under low velocity impact damage, failure mechanism of X-cor sandwich structure is complex. Failure behavior of X-cor sandwich structure at different energy stages was analyzed, and the effects of the volume fraction of Z-pin implant and the density of the foam core on the failure behavior were also discussed. Z-pin diameter of specimens in low speed impact test was 0.5 mm, and the implantation angle was 22°, and the type of foam and Z-pin implant volume fraction in the experiment was variable.The results show that under 6 J impact energy, the impact energy is mainly absorbed by the panel's delamination. The sandwich contained Z-pin is beneficial to reduce the delamination area, while the delamination area of blank sample increases by 45.1%. The foam density has little effect on the delamination area. The Z-pin fails under 12 J impact energy. The residual compressive strength ratio increases first and then decreases with the increase of volume fraction of Z-pin. The sample has the highest residual compressive strength ratio when the volume fraction reaches 0.42%. As the foam density increases, the residual compressive strength ratio increases. When the energy reaches 18 J, shear crack appears in the foam core, and the crack absorbs most of the energy. The weaker the foam core, the larger the residual compressive strength ratio is, and the more the volume fraction of Z-pin implanted, the lower the residual compressive strength ratio is. The low velocity impact model is also established by numerical simulation, and the result of impact damage is directly transferred and applied to study the residual strength model; the result obtained is 25%~29% higher than the experimental value.

Preparation of Ta/W Composite by CVD

Xiaohong QI, Xu ZHENG, Hongzhong CAI, Shaopeng LIU, Changyi HU, Yan WEI

2017, 37(2): 38-43.

[Abstract](3422) [FullText HTML] (1241) [PDF 5684KB](16)

Abstract:
The Ta/W composites with 10%W, 13%W and 18%W were prepared by chemical vapor deposition (CVD). The properties of Ta/W composites were investigated by optical microscopy (OM), scanning electron microscopy (SEM) and tensile test. The results show that it is possible to prepare Ta/W composites with different W volume fractions by CVD, and the actual densities of the composites are more than 99.4% of the theoretical density. Both Ta and W layers have columnar grain structures, and the more close to the interface, the more fine the grains are. The mechanical properties of CVD Ta/W are better than those of CVD Ta or CVD W. After hot treatment (1600 ℃×2 h), the diffused layers of the composites have become more wider and the mechanical properties are increased remarkably, and the tensile strength of the CVD Ta/W composite with 18%W is 660 MPa.

Preparation and Thermal Shock Performance of ZrO₂/NiCrAlY Thermal Barrier Coating

Lingshuang WANG, Guojian CAO, Guangze TANG, Wanjiao XU, Xinxin MA

2017, 37(2): 44-48.

[Abstract](2747) [FullText HTML] (1338) [PDF 16700KB](19)

Abstract:
Electric spark deposition (ESD) combining with micro-arc oxidation (MAO) were employed to fabricate ZrO₂/NiCrAlY thermal barrier coating (TBC) on GH4169 substrate. Firstly, a NiCrAlY coating with thickness of 250 μm was deposited on GH4169 substrate by ESD. Secondly, a Zr coating with thickness of 150 μm was deposited on NiCrAlY coating followed by MAO of the Zr coating. The thermal shock performances of the coatings under different temperatures were investigated. The results indicate that the thermal cycle numbers of the coatings at 750℃, 850 ℃ and 950℃ are 51, 32, and 19 respectively.

Heat Resistance of Epoxy-modified Silicone/Al-Sm₂O₃ Composite Coatings

Weigang ZHANG, Lianhai XUE, Yonggui WANG, Huixiao LU

2017, 37(2): 49-54.

[Abstract](2791) [FullText HTML] (1233) [PDF 5644KB](13)

Abstract:
Epoxy-modified silicone/Al-Sm₂O₃ composite coatings with epoxy-modified silicone and Al & Sm₂O₃as adhesives and pigments were prepared through spraying method. The effect of heat treatment temperature and heat treatment time on the appearance, microstructure, near-infrared reflectivity, infrared emissivity and mechanical properties of the coating were systematically investigated. The results indicate that after heat treatment at 300 ℃ with 5 h, the appearance and microstructure of the coatings remain unchanged, and the emissivity and near-infrared reflectivity at 1.06 μm are as low as 0.607 and 64.7% respectively; hardness, adhesion strength, and impact strength are maintained at 4 H, 1 grade and 50 kg·cm respectively. After heat treatment at 250 ℃ with 100 h, the appearance and microstructure of the coatings remain unchanged, and the emissivity and near-infrared reflectivity at 1.06 μm are as low as 0.624 and 67.1% respectively; hardness, adhesion strength and impact strength are maintained at 4 H, 1 grade and 50 kg·cm respectively.

Fabrication of Aluminum Foam by Space-holder Method and the Energy Absorption Properties

Xudong YANG, Jian SHI, Jie CHENG, Yajun CHEN, Fusheng WANG

2017, 37(2): 55-62.

[Abstract](3528) [FullText HTML] (1349) [PDF 14898KB](17)

Abstract:
Aluminum foam was fabricated by space-holder method with carbamide particles as space-holder material. The effects of forming temperature, porosity and diameter of pores were investigated systematically. During this process, the electronic universal testing machine combined with digital image correlation (DIC) technique was used to test the properties. The results show that the porosity and diameter of pores can be well controlled by space-holder method. The best sintering temperature of forming Al foam is 650 ℃. Under this sintering temperature, the compressive yield strength reaches 10.7 MPa. With the decrease of pore porosity, both of the compressive yield strength and platform stress increase, so the energy absorption of foam is improved remarkably. When the diameter of pores is below 2.0 mm, the energy absorption of foam is improved slightly with the increase of Al foam diameter. DIC technology can be used directly to characterize the mechanical behavior of foam material, which has a good engineering application prospect.

Mechanical Properties of Domestic T700 Grade Carbon Fibers/QY9611 BMI Matrix Composites

Guoli LI, Gongqiu PENG, Yingfen WANG, Fuyuan XIE

2017, 37(2): 63-72.

[Abstract](3518) [FullText HTML] (1312) [PDF 5751KB](42)

Abstract:
The morphologies, surface energies and surface chemical properties of the domestic T700 grade carbon fiber and the T700S carbon fiber were characterized by using scanning electronic microscopy (SEM), inverse gas chromatography (IGC) and X-ray photoelectron spectroscopy (XPS) respectively.The mechanical properties of the two carbon fibers/QY9611 composites were also discussed. The results indicate that the surface properties of carbon fibers have an important influence on the interfacial properties of composites. The interfacial properties of domestic T700 grade carbon fibers/QY9611 composite at room temperature/dry conditions are superior to T700S/QY9611 composite. The toughness of domestic T700 grade carbon fibers/QY9611composite is outstanding as well. The value of CAI has reached the level of foreign advanced composite IM7/5250-4. After hydrothermal treatment, the interfacial strength of domestic T700 grade carbon fibers/QY9611 composite is equal to that of T700S/QY9611 composite. It shows that domestic T700 grade carbon fibers/QY9611 composite has good hydrothermal-resistant properties.

Quasi-Static Crushing Simulation Research and Failure Mode Analysis of Composite Thin-Walled C-Channel Specimen

Jiang XIE, Congyao MA, Jian ZHOU, Haolei MOU, Zhenyu FENG

2017, 37(2): 73-80.

[Abstract](3519) [FullText HTML] (1398) [PDF 4143KB](17)

Abstract:
To study the crushing energy-absorbing characteristics and failure mode, the multi-shells finite element model of composite thin-walled C-channel specimen was established based on the quasi-static crushing test results. The simulation results show that the delamination failure, local buckling and beam bending failure of C-channel specimen can be simulated with the multi-shells finite element model. The load-displacement curve well fits the test results, and the deviation of initial peak load (F_max), specific energy absorption (E_s) and crushing mean load (F_mean) is small compared with the test results. The initial peak load of C-channel specimen is larger and the load efficiency is lower, so it is necessary to further reduce the initial peak load by the design optimization.

A New Method of Fatigue Life Prediction for Notched Specimen

Dan JIN, Zhifei GOU

2017, 37(2): 81-87.

[Abstract](2974) [FullText HTML] (1404) [PDF 1364KB](27)

Abstract:
The simulations of the notched specimens under multiaxial loading were conducted by finite element method. The simulation results show that the stress gradient increases with the decrease in notch radius for the same strain path. The equivalent strain method is used to predict the fatigue life based on the strain at the notched root. The prediction results are more conservative with the decrease in notch radius. The effective distance is determinated by the stress gradient method, and the effective distances are decreased with the decrease of notch radius for the same strain path. The fatigue life is predicted based on the strain at the effective distance, and the predictions are scattered and unconservative. Combining the test results and simulations, a new method determinating the effective distance is presented considering the strain gradient. Most prediction results are in a factor-2 scatter band.

Research Status and Developing Trend of Space Tribology and Tribological Materials

Aiwen ZHONG, Pingping YAO, Yelong XIAO, Haibin ZHOU, Taimin GONG

2017, 37(2): 88-99.

[Abstract](3598) [FullText HTML] (1362) [PDF 3264KB](67)

Abstract:
The harsh space environment and its influence on the performance of space tribological materials are reviewed. The effects of the harsh space environment on the friction and wear mechanisms of friction materials, anti-wear materials and anti-friction materials are analyzed respectively. Space friction materials which are often used in space docking system and space manipulator should have stable friction torque and excellent adhesive wear resistance. Space anti-wear materials are mainly used in the space bearings, gears and seal parts. For example, The metal elements (e.g. Ce, Cr, Mn, Mo, Nb, W) and solid lubricants are often added for Fe-Al intermetallics to restrain creep at high temperature; the wear resistances of Ti and its alloys are often improved by surface modification; anti-wear coating which has a proper associativity with the matrix can improve the wear resistance of the materials. Space anti-friction materials mainly refer to lubricants and self-lubricating materials which can reduce friction coefficient of the materials, such as soft metals, polymer materials, some oxides, fluorides and sulfides. With the development of aerospace science and technology, it is highly demanded that the novel tribological materials with high performance should be developed for space applications, and the database of tribological materials should be built, in order to meet the international challenge of development of space technology.

2017 Vol. 37, No. 2