航空材料学报

2015-06-Catalog

2015, 35(6): .

[Abstract](1332) [PDF 2740KB](6)

Abstract:

Interface Reaction between DD6 Single Crystal Superalloy and Ceramic Mold

Jian-sheng YAO, Ding-zhong TANG, Xiao-guang LIU, Xin LI, Li-li WANG, Chun-xiao CAO, Fang-zheng DING, Hao CHEN

2015, 35(6): 1-7.

[Abstract](2694) [FullText HTML] (1418) [PDF 1646KB](57)

Abstract:
The interface reaction between DD6 single crystal superalloy and ceramic mold was investigated by optical microscope (OM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results show that the reaction products are Al₂O₃ and HfO₂, and small amount of Ta was released at the same time. The thickness of the reaction layer is 5-6μm. As the reaction products are concentrated in the interface of alloy/mold, the oxidation reactions were inhibited. The contact angle between DD6 alloy and ceramic mold is 145-150° at high temperature. The capillary action is decreased by reducing the porosity of the ceramic mold, and the interface reaction can be inhibited simultaneously.

Strengthening Mechanism of Isothermal Forged Mg-10Gd-2Y-0.5Zn-0.3Zr Alloy during Ageing Process

Xiu-zhu HAN, Jin-cheng PANG, Xu-hu ZHANG, De-bin SHAN, Chu-ming LIU

2015, 35(6): 8-13.

[Abstract](2543) [FullText HTML] (1279) [PDF 3150KB](12)

Abstract:
The microstructures of the initial forged, isothermal forged and peak-aged Mg-10Gd-2Y-0.5Zn-0.3Zr alloy were analyzed by optical microscopy and scanning electric microscopy. The results show that the isothermal forging process has little effect on the refinement of microstructure compared with that of the initial forged alloy, but the dispersed precipitation of great amount of the second phases in the matrix mainly causes the strength slightly increased for the isothermal forge alloy. During the ageing procee of the alloy at the temperature of 200℃, more and more small particles and lamellar strengthened phases are precipitated in the matrix along with the extension of the ageing time, its optimum ageing process is 200℃/60h. The ultimate tensile strength, tensile yield strength and elongation of the peak-aged alloy at 200℃ are 379 MPa, 245 MPa and 4.6% respectively. The main strengthening mechanism of the peak-aged alloy is ascribed to the dispersed precipitation of the LPSO phases and β' phases.

Microstructure and Mechanical Properties of Al-Cu-Mg Alloy Prepared by Cryomilling Combined Powder Metallurgy

Tian-bing HE, De-sheng CHU, Peng-jun TANG, Xing-yuan WANG, Xiao-lei HE, Pei-yong LI, Ren-wei HU

2015, 35(6): 14-19.

[Abstract](2564) [FullText HTML] (1333) [PDF 3188KB](15)

Abstract:
Al-Cu-Mg alloy powder fabricated by a unique technique which combined rapid solidification and cryomilling together was consolidated under cold pressing and hot extrusion, then treated with solid solution and nature ageing. Microstructure evolution and mechanical properties were investigated by XRD, SEM and TEM, etc. The results show that the morphology of as-atomized Al-Cu-Mg alloy powder evolves from sphere to flake after cryomilling for 4h, and CuAl₂ and Al₂CuMg phases disappear and super-saturate into α (Al). The as-extruded material exhibits densified structure with relative density of 98.6%.After heat treatment, the average grain size of alloy is 900nm, and a lot of dispersive GP zones and S″ phases precipitate during natural ageing period. The tensile and yield strength of T4 condition alloy are 526MPa and 397MPa respectively, also exhibiting good ductility(δ=15%).The strengthening mechanisms can be attributed to fine crystal and precipitation strengthening.

Research on Molding Pressure of Advanced Pultrusion for Half Lenticular Tube

Bo-wen JU, Jun-wei QI, Tao LI, Jing ZHU, Jun XIAO

2015, 35(6): 20-26.

[Abstract](2869) [FullText HTML] (1248) [PDF 9301KB](12)

Abstract:
The effects of different shapes and thicknesses of silicone rubber on the contact pressure distribution during advanced pultrusion processing for half lenticular tube were studied using finite element method, and the dispersion coefficient was used to evaluate the uniformity of the contact pressure. The results indicate that the dispersion coefficient decreases and then increases with the increase of vertical thickness of offset surface silicone rubber or vertical thickness of translated surface silicone rubber at the thickness range from 5mm to 50mm, which means the uniformity of the contact pressure improves initially and then declines. Also when the vertical thickness of translated surface silicone rubber is 10mm, the dispersion coefficient is the lowest, only 0.8%, which indicates that the contact pressure is the most uniform.

Investigation on Glass Fiber Reinforced Aluminum Laminates under Pin-bearing Load

Yue ZHUO, Zhi-dong GUAN, Ri-ming TAN, Jun GUO

2015, 35(6): 27-34.

[Abstract](3007) [FullText HTML] (1317) [PDF 5557KB](12)

Abstract:
Damage initiation and carrying capacity of glass fiber reinforced aluminum (GLARE) laminates under bearing load were studied. Bearing behaviors of GLARE laminates were experimentally investigated through three methods:C-scan, micro-photography and scanning electron microscope. The initiation and evolution of the damage of the laminates were studied. The effects of the lay-up on the bearing behaviors of the laminates were also discussed. The plastic deformation of the metal, the buckling of the fiber, the crack of the matrix and delamination on the hole edge during the experiments were observed and compared. The results show that the damage of those laminates initially occurred is due to the plastic deformation of metal layers. When the deformation progresses, the damage evolution, failure mode and carrying capacity are influenced by the lay-up of laminates. The results can provide a guidance for the connection structure design of GLARE laminates.

Research on Forming Limits of Superalloy GH600 Sheet

Cheng-xiang ZHANG, Ming-he CHEN, Xiao-jing LEI, Si-jia HU, Ya-feng WU

2015, 35(6): 35-40.

[Abstract](2567) [FullText HTML] (1391) [PDF 3024KB](12)

Abstract:
The forming limit diagram(FLD)of superalloy GH600 sheet was determined through the experiment, and the function model was built. The deep drawing processes and cupping processes were simulated by using the function model of FLD based on the experiment, and the FLD was automatically produced by Keeler formular in DYNAFORM software as broken criterion. The deep drawing and cupping tests were also performed in order to validate simulated results. The results show that the auto Keeler FLD is quite different from the experimental data. When simulating with DYNAFORM, the breaking problem can be predicted more precisely in the forming process of GH600 by using the FLD based on experiment as the broken criterion.

Microstructure Evolution of GH536 Ni-based Superalloy Welded by GTAW

Zhen-wei WEI, Chun-hu TAO, Yu-li GU, Chang-kui LIU, Shi-yu QU

2015, 35(6): 41-47.

[Abstract](2572) [FullText HTML] (1378) [PDF 4982KB](17)

Abstract:
Microstructure of GH536 GTAW (Gas Tungsten arc welding) joint was analyzed bystereomicroscope,Optical microscope,SEM and EDS. The results show that solution-treated GH536 consists of γ matrix,a large volume fraction M₆C and a few M₂₃C₆. After welding, a large volume fraction of tiny M₆C precipitates in the matrix is discontinuously dispersed in the grain boundaries and twin boundaries, and the original carbides become bigger. Microstructure in HAZ(heat affected zone) consists of three regions:Carbides exist in the shape of coarse "island chain" morphology nearby based metal. In the middle region, partial carbides are redissolved into the matrix, appearing "network chain" morphology. The carbides are poor in the region nearby the fusion line. In the welded seam, the carbides are precipitated in grain boundaries and interdendritic regions. The solidification from edge to center has three stages:At start, cellular structures are formed without epitaxial growth, and growth direction is perpendicular to the fusion line. At intermediate stage, crystalline growth is columnar-dendritic, and grain size gets bigger. At the final stage, equiaxed dendritic structures are formed in the center. In the welding process, the elements in the substratehavenot been lost.

Effect of Heat Treatment on Mechanical Properties of Commercial Pure Titanium Self-piecing Riveted Joints

Yi LU, Xiao-cong HE, Yi-feng WANG, Bao-ying XING

2015, 35(6): 48-52.

[Abstract](3089) [FullText HTML] (1251) [PDF 2715KB](7)

Abstract:
The stress relief annealing and quenching were applied to treat the whole commercial pure titanium self-piecing riveted (SPR) joints. The static tensile test was used to test the joints before and after treatment. The effects of heat treatment on the mechanical properties and the failure mechanism of the joints were analyzed. The results show that the two kinds of heat treatment processes can improve the static strength of the commercial pure titanium SPR joints. The stress relief annealing can improve the static energy absorption ability of the joints, and quenching has little impact on the static energy absorption ability of the joints. The failure modes of the three joints are the rivet being pulled out or cracked. The fracture morphology of the rivet in the joint that is not treated presents the characteristic of intergranular brittle fracture, the rivet in the joint that is treated by stress relief annealing shows the characteristic of ductile fracture, and the rivet in the joint that is treated by quenching displays the characteristic of quasi-cleavage fracture. The stress relief annealing is the preferable heat treatment of the commercial pure titanium SPR joints.

Effect of Surface Treatment on Bond Joint Strength of TB8 Titanium Alloy and Composite Material

Chun-yan WANG, Xi-wen ZHOU, Qun HUANG, Hai-hua HONG

2015, 35(6): 53-59.

[Abstract](2625) [FullText HTML] (1281) [PDF 4136KB](15)

Abstract:
In order to investigate the effect of surface treatment on the bond joint strength of TB8 titanium alloy and composite material, surface morphology analysis, bond joint experiment of TB8 titanium alloy and composite material as well as peel strength testing was carried out after that the laser texturing and caustic soda solution anodizing were performed on the surface of TB8 titanium alloy sample. The results show that both laser texturing and caustic soda solution anodizing can improve the bond joint strength of TB8 titanium alloy and composite material. The max peel strength between the composite material and the laser textured TB8 titanium alloy sample is 4.20N/cm, while the max peel strength between the composite material and the caustic soda solution anodized TB8 titanium alloy sample is reached to 5.99N/cm, indicating that the caustic soda solution anodizing is more appropriate for improving the bond joint strength of TB8 titanium alloy and composite material.

Influence of Doping On Properties of Cu/SnO₂ Contact Materials

Wen-jie ZHAO, Jun-bo WANG, Rui-juan WANG, Yan-long WANG, Song-tao LIU, Ze-tao HU

2015, 35(6): 60-64.

[Abstract](2897) [FullText HTML] (1270) [PDF 3331KB](8)

Abstract:
Cu/SnO₂ electric contact material was prepared by high energy ball milling process. X-ray diffraction (XRD) was carried out to evaluate the effect of Cu/SnO₂ mixed powder, and scanning electron microscope(SEM) was used to observe the micro morphology and the arc erosion morphology of electric contact material. Electrical conductivity and hardness of electrical contact materials were also tested. The effects of mixing time, sintering temperature and doping on the properties of Cu/SnO₂ electric contact materials were also studied systematically. The results show that Cu/SnO₂ electric contact materials have the best physical properties when Cu/SnO₂ mixed for 4h and sintered at 850℃.The electrical conductivity is 49.0% IACS, and hardness is reached 122.0HV. The arc erosion of Cu/SnO₂ electric contact material with La₂O₃ is slight, showing good resistance to arc erosion.

Analysis of Conjugate Flow Field between Cooling Film and Thermal Barrier Coating

Jia-li LI, Yu-zhang WANG, Xing WANG

2015, 35(6): 65-70.

[Abstract](3061) [FullText HTML] (1258) [PDF 3137KB](9)

Abstract:
To study the effects of pores' micro-structure of thermal barrier coating on its surface flow field, the micro-structure and grid of the coating were generated by Matlab through grey processing and pixel identifying based on layered and columnar thermal barrier coating. The microscopic flow models between the cooling film and thermal barrier coating were developed by Lattice Boltzmann method. The results indicate that the micro-structure of thermal barrier coating has a great influence on the gas flow between the cooling film and the coating. Disturbance appears in the vertical direction of the inlet flow, and it will affect the stability of the film. Weak flow exists in the pores of columnar coatings, and a vortex flow generates on the conjugate surface. The pulsation of vertical velocity of the gas film of layered coating is more severe than that of columnar coating because of the rough surface.

Initiation and Propagation of Small Fatigue Crack of GH4169 Alloy at 650℃

Nan WU, Xian-cheng ZHANG, Zheng-dong WANG, Shan-dong TU

2015, 35(6): 71-76.

[Abstract](2711) [FullText HTML] (1335) [PDF 4038KB](21)

Abstract:
The initiation and propagation behavior of small fatigue crack of GH4169 alloy at 650℃ were studied. The SENT (single-edge-notch-tension) specimen was used in fatigue test. The frequency was 0.5Hz and the stress ratio was kept to be 0.1. The replica method was used to measure the crack length. Results show that only one main crack initiated from the inclusion is observed from the root of the notch. The life of small crack growth is more than half of the total fatigue life of specimen. The small fatigue crack is prone to propagate into the interior of specimen with semi-elliptical shape, which can be reflected from the fractography analysis. Combined with the observation from the crack growth rate curve, it can be concluded that the crack growth rest plays an important role on the transition of fracture mode. When the crack propagation mode completely is transformed from transgranular to intergranular, the crack growth rate will be increased rapidly, leading to the final fracture of the specimen.

Accelerated Equivalent Relationship between Natural Exposure and Accelerated Experiments of Aircraft Coating Based on Gloss Loss

Peng WANG, Ping JIN, Xiao-ming TAN, De WANG

2015, 35(6): 77-82.

[Abstract](2447) [FullText HTML] (1215) [PDF 2077KB](14)

Abstract:
According to the aging problem of the surface coating of aircraft structure, two models for accelerated equivalent relationship followed Logarithmic normal distribution and Weibull distribution were developed by Arrhenius formula based on the failure criterion of gloss loss. To verify the rationality of theoretic models, natural exposure test and accelerated aging test were conducted, and the life of the coating was predicted by two models. The results show that the predicted life of Logarithmic normal distribution is closer to the real value and more credible than that of Weibull distribution.

Infrared Flash Thermographic Nondestructive Testing of Defects in Thermal Barrier Coating

Ying-tao LIU, Ren-de MU, Guang-ping GUO, Dang-gang YANG, Jia TANG

2015, 35(6): 83-90.

[Abstract](2615) [FullText HTML] (1226) [PDF 3456KB](16)

Abstract:
To keep track of the process of generation and development of cracks and debonding defects in thermal barrier coating, a set of test pieces with thermal barrier coating deposited on both sides were made and went through hundreds of working cycles. Infrared thermographic nondestructive testing(NDT) experiments were made on those pieces before working cycles and after different number of working cycles. Abnormal areas found in the pieces were analysed by SEM observation on cross sections, and small cracks were identified. The experiments on test pieces with natural defects and artificial defects were made to evaluate the ability of infrared thermographic NDT. Based on those experimental results, it is concluded that small cracks which cannot be observed the from the coating surface can be identified in infrared flash thermographic NDT, and debonding areas which are less than 0.5 mm in diameter can also be detected by using the NDT technology. Infrared flash thermography is suitable for NDT of the defects in thermal barrier coating.

Microwave Evaluation of Direction and Bending Defect of Carbon Fiber in Composite Material

Yu-e YANG, Tian-ting YAN, Bao-sheng REN

2015, 35(6): 91-96.

[Abstract](2800) [FullText HTML] (1261) [PDF 2116KB](14)

Abstract:
By studying the transmission characteristics of microwave in composite material, N5225A network analyzer was used to detect carbon fiber direction and bending defect. The amplitudes and phases of the reflection coefficient are the characteristic parameters to detect carbon fiber in composite material. The results show that in 30-40GHz, both differences of the reflection coefficient amplitudes and phases increase along with the increase of operating frequency. At 40GHz, the amplitude difference and the phase difference are 48° and 0.37 respectively. At 36GHz, the bending defect is characterized by the phase difference, the maximum of which is 2.65 degrees. At 38GHz, the bending defect is characterized by the amplitude difference, the maximum of which is 0.004. The sensitivity to detect fiber direction is far greater than that to detect fiber bending defect.

2015 Vol. 35, No. 6