航空材料学报

Nucleation of β/α Phases in Undercooled Ti-48(at%)Al Peritectic Alloy

LI Man, XUE Xiangyi, HU Rui, ZHANG Tiebang, ZHONG Hong, LI Jinshan

2012, 32(2): 1-7.

[Abstract](2298) [PDF 2133KB](524)

Abstract:
The Ti48(at%)Al peritectic alloy was solidified at various bulk undercooling using electromagnetic levitation method. The maximum undercooling of the alloy melt was up to 295K. Detailed thermal histories were acquired during experiments using optical pyrometry. The solidification microstructures were investigated by OM. Solidification and other hightemperature transformation pathways were deduced from the thermal data and microstructural analysis. The dependence of nucleation between the primary phase and the secondary phase on the undercooling was identified by analyzing the recalescence behaviour and microstructure, and investigated systematically by using the classical solidification theory, the negentropic model and the transient nucleation theory. The interfacial critical work of nucleation, steady state nucleation rates, incubation time and time dependent nucleation rate of two phases (bcc) phase and (hcp) phase were calculated , and the calculated results were analyzed by comparing with the experimental data . The results are as fellows: phase is always prior to nucleate from all undercooled(295K) melt below the cooling rate ~10K/s .

Withdrawing Rate on Low Cycle Fatigue Properties of Single Crystal Superalloy DD6 at 650℃

LIU Weiwei, TANG Dingzhong, LI Jiarong, LIU Shizhong, XIONG Jichun

2012, 32(2): 8-12.

[Abstract](1980) [PDF 3727KB](361)

Abstract:
The bars of single crystal superalloy DD6 were prepared with withdrawing rates of 2mm/min, 4.5mm/min, 7mm/min.The low cycle fatigue properties of alloy with different with drawing rates were studied comprehensively at 650℃.The fatigue fracture morphology and microstructure were investigated using SEM and TEM. The results show that with the increasing of withdrawing rate, the size of precipitates decreases and quadratic dendrite arm spacing developed gradually. Primary dendrite arm spacing is little related to withdrawing rate. Alloy with the withdrawing rate of 4.5mm/min has the longest low cycle fatigue among the withdrawing rates. It was founded that DD6 alloy exhibited cycle stability at most strain amplitude. The fatigue crack favorably initiated at the subsurface，and reduced along with the strain amount. The fatigue propagation characteristics of the first stage changed from cleavagelike fatigue facet into ragged fatigue facet.Fatigue crack extended along one or more {111} sliding surfaces.

Effects of HIP Temperature on Microstructure and Mechanical Properties of K447A Superalloy

LI Ailan, TANG Xin, CAO Lamei, GAI Qidong

2012, 32(2): 13-19.

[Abstract](1862) [PDF 7062KB](376)

Abstract:
（Science and Technology on Advanced High Temperature Structural Materials Laboratory, Beijing Institute of Aeronautical Materials， Beijing 100095, China)Abstract： The effects of HIP temperature on microstructure and mechanical properties of superalloy were studied. The results show that with the increasing of HIP temperature, the microstructure and mechanical properties are changed obviously , i.e. the microporosity of the alloy is eliminated, the change of the size and shape of the primary MC carbide phase shows the fact of the carbide refinement and spheroidization, the amount of eutectic phase decreases and the amount of fine regular phase increases. The grain boundary of the alloy is not good due to the increase of the size of phase after the treatment of the 1230℃HIP. The stress rupture life of 980℃/200MPa is improved greatly after the treatment of 1185℃HIP, 1195℃HIP, 1210℃HIP. However, the stress rupture life of 760℃/724MPa is improved after the treatment of 1210℃HIP. Hence, the best HIP temperature is 1185-1210℃ under the condition of 180MPa/4h.

Study on Simulation of Hot Processing Behavior of B93 Aluminum Alloy

LI Jinlong, JIANG Feng, JIAN Haigen, CHEN Yizhao, XU Yanping

2012, 32(2): 20-25.

[Abstract](1874) [PDF 3041KB](445)

Abstract:
LI Jinlong,JIANG Feng,JIAN Haigen,CHEN Yizhao,XU Yanping(Institute of Material Science and Engineering, Central South University,Changsha 410083, China)Abstract： The hot processing behavior of B93 aluminum alloy under various deformation temperature and strain rate was studied by Gleeble 1500 thermal simulator.The processing map was calculated according to the dynamic material model.The instability zones of flow behavior was obtained by the maps.The results show that the microstructure of alloy is influenced by deformation temperature and strain rate，the flow stress values decrease with the rise of temperature and increase with the rise of strain rate. And the optimum hot processing parameters were also attained by the maps,which the deformation temperature was around 420℃ and the strain rate was 0.001 s-1.

Plotting of Isothermal Transformation Curves of 6005 Aluminum Alloy Profiles and Their Application

WANG Gang, YIN Zhimin, ZHOU Xiang, SHANG Baochuan

2012, 32(2): 26-31.

[Abstract](1953) [PDF 1579KB](296)

Abstract:
The timetemperaturetransformation (TTT) and timetemperatureproperty (TTP) curves of 6005 aluminum alloy were determined by isothermal transformation research. And the microstructure transformation during isothermal treatment was studied by XRD，TEM and Avrami equation. The results show that the sensitive temperature range of 6005 aluminum alloy is 280-420℃ with the nose temperature of 340℃. Microstructure observation indicates that the supersaturated solid solution decomposes and precipitates during initial stage of isothermal holding . With the prolonging of isothermal time, and form in the alloy. 6005 alloy has different transformation kinetics equations when treated at different isothermal treatment temperatures. According to the results, speeding up the cooling rate in the quench sensitive section to reduce the precipitation of equilibrium phase is meaningful, and at higher and lower temperature, decreasing the cooling rate is helpful to decrease the residual stress.

Investigation of TwoStep Aging Treatment of New Type AlZnMgCu Alloy

LU Zheng, GONG Peng

2012, 32(2): 32-37.

[Abstract](1904) [PDF 2621KB](297)

Abstract:
TV (In GP zones,the nucleation below this temperature is not relying on vacancy content.), and TC (In GP zones, the nucleation is unable to be formed above this temperature.) of a new type AlZnMgCu alloy extruding plate were determined by hardness test. The results indicate that TV is between 130℃ and 140℃ and TC is about 170-180℃. Using these data, the first aging temperature of 120℃ and the second aging temperature of 165℃ were selected. After aging at 120℃/4h+ 165℃/8h, the tensile strength, yield strength, elongation, fracture toughness and electrical conductivity in the longitudinal direction of the alloy is 617MPa, 590MPa, 13.5%, 41.6MPam and 39.1%IACS respectively. The alloy is a Al alloy of 600MPa level strength with good combination property after twostep aging treatment.

Nanocrystalline Aluminum Powder Prepared via Cryomilling

LI Jiongli, LI Shasha, LI Wei, XIONG Yancai

2012, 32(2): 38-42.

[Abstract](1763) [PDF 1961KB](382)

Abstract:
Nanocrystalline aluminum powders was prepared by cryomilling. The chemical composition, morphology and particle size, microstructure of the aluminum powders before and after cryomilling were studied by inductive coupled plasma atom emission spectrometry (ICP), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) respectively. The results indicate that the distribution of the particle size of aluminum powder changes from broadening to narrowing, and to broadening again with the increase of the milling time, which is concerned with comprehensive effects of the comminution and welding. The mechanism of evolution of dislocation cells dominates the grain refinement of the aluminum powder in the initial cryomilling period, while in the later cryomilling period the grain refinement of the aluminum powder is in the charged of the mechanism of fracture and cold welding.

Abrasion Resistance Coatings Prepared from Methyltrimethoxysilane and Tetraethoxysilane on Polycarbonate Substrates

CHEN Yu, LIU Li, ZHAN Mao, ZHOU Ke

2012, 32(2): 43-48.

[Abstract](2344) [PDF 2121KB](383)

Abstract:
The abrasion resistance coatings prepared through the solgel process with MTMS as the film forming material and tetraethylorthosilane (TEOS) as the inorganic reinforcing component were applied on the bisphenolA polycarbonate. It is demonstrated that the cross linked network structure of SiOSi is formed at the surface of PC. The relationship between abrasion resistance and component content of the coating were investigated by comparing the optical performance before and after the abrasion test. The result shows that PC coated with the MTES/TEOS possesses much better abrasion resistance than uncoated PC. When the component of the coating is MTMS∶TEOS=2∶1，the coating exhibits the best abrasion properties. The haze of PC coated with the optimal coating is only 13.22% after 500 times abrasion, while that of uncoated PC is rised up to 56.21%.

Effect of Cure Temperature on Mechanical Properties of Composite Reinforced by Ramie Fiber

ZHAO Yunfeng, ZHANG Jihua, YOU Shaoxiong

2012, 32(2): 49-53.

[Abstract](1720) [PDF 859KB](375)

Abstract:
The effect of cure temperature on mechanical properties of unidirectional ramie fiber reinforced composite was studied and the comparative research about mechanical properties of composites reinforced by plain ramie fiber, unidirectional ramie fiber and glass fiber was undertaken. Unobvious change of tensile and flexural properties was detected, when the epoxy resin 3233 was cured for 2h at 120℃,140℃ and 180℃. The ramie fiber reinforced composite had similar mechanical properties after cured for 2h at 120℃, and 140℃, however the composite after cured for 2h at 180℃ had lower tensile strength and flexural strength and comparative modulus. The mechanical properties of unidirectional ramie fiber reinforced composite were much better than those of plain ramie fiber reinforced composite, such as that the compressive strength and compressive modulus of unidirectional ramie fiber reinforced composite uRa mie3233120 are 154.0 MPa and 35.6 GPa respectively, however the compressive strength and compressive modulus of plain ramie fiber reinforced composite fRamie3233120 are 95 MPa and 9.2 GPa respectively. The unidirectional glass fiber reinforced composite has much better strength, comparative to ramie fiber reinforced composite.

Storage Stability of Vulcanized AcrylonitrileButadiene/Phenolic Resin/Hindered Phenol AO80 Damping Rubber

ZHAO Yunfeng, ZHANG Jihua, YOU Shaoxiong

2012, 32(2): 54-58.

[Abstract](1823) [PDF 1320KB](298)

Abstract:
3,9bis［1,1dimethyl2{(3tertbutyl4hydroxy5methylphenyl)propionyloxy}ethyl］2,4,8,10tetraoxaspiro［5,5］ und ecane (AO80) and the phenolic resin (PR) were added into the acrylonitrilebutadiene rubber (NBR) to prepare the vulcanized NBR/PR/ hindered phenol rubber. The structure of the vulcanized rubber was characterized by DSC, FTIR, DMTA and SEM. And its damping and mechanical mechanism was investigated in detail. The results show that the microscopic structure of vulcanized rubber include the networks of intermolecular hydrogen bonds between NBR and AO80 molecules, the nonbonding complexation of PR in NBR, the molecular aggregation of AO80 (AO80 rich phase) and NBR segments incorporated into the AO80 molecular aggregations besides the vulcanized networks of NBR. These complex molecular interactions lead to the increase of internal friction, and thus vulcanized rubber obtain good damping properties. However, with the increasing of deposited time, the AO80 aggregates and crystallines in the rubber, which affects the stability of damping properties of the rubber.

Research on WaterSorption Behaviors of T700/9916 Composite Laminates

CAO Su, WANG Bo, JIAO Guiqiong

2012, 32(2): 59-64.

[Abstract](1908) [PDF 1883KB](331)

Abstract:
The absorption of water in carbon fiber reinforced polymer matrix composites (CFRP) in hydrothermal environment was investigated. Watersorption experiments were performed in temperaturecontrolled water bath at 70℃ and different conditions of relative humidity (98%, 91%, 84% R. H.) at 70℃ according to standards, and the watersorption curves were obtained. When the relative weight gain of the immersed specimens was reached equilibrium, the others were still increased linearly.The experimental data were analyzed by Fickian diffusion model. The analytical results exhibited a much lower rate of weight gain than experimental data. Diffusivity and solubility were calculated by the combination of experimental results and finite element simulation. Simulations were carried out under different hydrothermal conditions. The simulation results were coincided with the experimental data. The longterm sorption kinetics curves and water distribution within the specimen were obtained.

LiquidPhase Oxidation Modification of PANBased Carbon Fiber Surface

YUAN Hua, WANG Chengguo, LU Wenbo, ZHANG Shan, CHEN Yang, YU Mei

2012, 32(2): 65-68.

[Abstract](1950) [PDF 951KB](382)

Abstract:
The change of the microstructure of carbon fiber with liquidphase oxidation modification was investigated under different treatment conditions by Raman spectroscopy (Raman), Infrared spectroscopy (IR), and Scanning electron microscope (SEM). The relationship between microstructure and mechanical properties of monofiber was also studied. The results indicate that surface etching increases surface groove. Acid treatment shows an obvious positive effect on the chemical modification of carbon fiber surface, it increases the grain boundary activity and surface acidic functional groups (C=O and OH), while the graphite microcrystalline decrease. The mechanical properties of the carbon fiber decline after acid treatment. The tensile strength decreases about 15% and 50% respectively, when the times for the liquidphase treatment are 60min and 120min.

Ablation Properties of 2D C/SiCZrB₂ Composite

TONG Changqing, CHENG Laifei, LIU Yongsheng, ZHANG Litong

2012, 32(2): 69-74.

[Abstract](1870) [PDF 7021KB](294)

Abstract:
2D C/SiC-ZrB2 composite was fabricated by combining chemical vapor infiltration, ZrB2 slurry infiltration and polymer infiltration and pyrolysis method. The ablation properties of the composite under oxyacetylene flame and 1800℃ methane combustion wind tunnel were studied. The results show that under the oxyacetylene flame environment, the linear ablation rate and the mass ablation rate of the 2D C/SiC-ZrB2 are 6.110-2mm/s and 1.010-2g/s respectively. The antiablation performance is improved by infiltrated ZrB2 particles into C/SiC matrix. Under the 1800℃methane combustion wind tunnel, the coating density plays a major role on the ablation behavior. At the same coating density, the mass ablation rate increases with the open porosity of the composites.The addition of ZrB2 to C/SiC has little effect on the antiablation performance.

Influences of Temperature on Microstructure and Oxidation Resistance of Carbon/Carbon Composites Modified by Solvothermal Process

HUANG Jianfeng, CAO Liyun, WANG Yaqin, WU Jianpeng, MI Qun, WANG Nina

2012, 32(2): 75-81.

[Abstract](1846) [PDF 3919KB](304)

Abstract:
In order to improve the oxidation resistance property of C/C composites, the C/C composites were modified by a novel solgel/solvothermal process. The suspension mixtures were prepared by mixing tributyl borate sol, ethanol, acetic acid and B2O3 powder. The asmodified C/C composites were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscope (EDS) and X-ray photoelectron spectroscopy (XPS) techniques. The influences of the solvothermal temperature on the phase, microstructure and antioxidation property of the asmodified composites were investigated. Results show that the surface of the C/C composites are covered by a coating consisted of molten B2O3 and the internal microholes are occupied by B2O3. With the increase of solvothermal temperature, and the density of the coatings also increases. The antioxidation property of the modified C/C matrix is effectively improved with the increase of solvothermal treatment temperatures from 353 K to 433 K. The mass loss of the modified C/C composites is only 4.09% after oxidation at 873 K in air for 16 h.

Preparation of _TiO2 UV Detector and Effect of Annealing Process on Photoelectronic Properties

QI Hongfei, LIU Dabo

2012, 32(2): 82-86.

[Abstract](1715) [PDF 1695KB](268)

Abstract:
TiO2 UV detector with excellent photoelectronic properties was prepared by RF magnetron sputtering and suitable annealing process. The effect of annealing process on the photoelectronic properties of TiO2 UV detector was investigated using SEM, XRD, and the detection of photoelectronic properties. It was found that the grain size of TiO2 was increased with the increase of annealing temperature, and the change of the photoelectronic properties of TiO2 UV detector is caused by the variation of the number of grain boundary and defect. After treated at 500C for 2 h, the photocurrent was nearly 2.5 orders of magnitude higher than the darkcurrent and the optical response at ultraviolet range was nearly 2 orders of magnitude higher than that at visible light region. The high sensitivity and visible blind properties of obtained UV detector had been achieved.

Preparation of OneDimensional Nanostructures BaFe₁₂O₁₉ and Study with Magnetic Manipulation

MIAO Lu, HUANG Ying, SU Wu

2012, 32(2): 87-92.

[Abstract](1673) [PDF 2668KB](266)

Abstract:
BaFe12O19 nanowires were prepared into homemade AAO by the sol-gel method. The diameter of nanowires is 40-60nm,and the length is 150-200nm. The composition,pattern and magnetic performance of the nanowires were characterized by XRD,FESEM and VSM. The rapping and ordering of the BaFe12O19 nanowires was carried out by magnetic force. The results show that the preferred direction of magnetization of BaFe12O19 is along to the nanowire direction,and the nanowires alignment is along the line of force, joint alpha and omega to chain.When magnetic field is parallel with the array of BaFe12O19 nanochain,BaFe12O19 nanowires possess high residual magnetization(Mr), specific magnetism(Ms) and maximum magnetic energy product(BH) m ,the coercivity(Hc) is increased from 3.98105A/m to 5.01105A/m, the specific magnetism S(ratio of Br and Hc) approaches to 0.9, all of this show that BaFe12O19 nanowires are the high density vertical magnetic recording medium.

Using Nonlinear Ultrasonic Test for Fatigue Damage of LY12 Aluminum Alloy

YAN Bingsheng, ZHANG Shixiong

2012, 32(2): 93-98.

[Abstract](1810) [PDF 3293KB](258)

Abstract:
For the problem of the LY12 aluminum early fatigue damage, a robust experimental procedure was researched. Using this system, the ultrasonic nonlinearity parameters of LY12 aluminum fatigue samples were measured. The experimental results show that there is a significant increase in linked to aluminum fatigue damage, before the fatigue life of 60%. Meanwhile, dislocation density change of LY12 aluminum fatigue samples is observed using erosion method, and the changes of nonlinearity parameter and dislocation density with fatigue cycles are consistent. Macromechanics, nonlinear ultrasonic testing and microscopic observation results show that ultrasonic nonlinearity parameters as the bridge between micro and macro can characterize the early fatigue damage, and predict fatigue life of metallic material.

2012 Vol. 32, No. 2