2014 Vol.34(2)

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2014, 34(2): 0-0.
[Abstract](64) [PDF 274KB](1)
Effect of Stress on Microstructural Stability of DD10 Single Crystal Superalloy
GU Huai-peng, CAO La-mei, XUE Ming, ZHOU Zhi-jun
2014, 34(2): 1-5. doi: 10.3969/j.issn.1005-5053.2014.2.001
[Abstract](181) [PDF 2816KB](3)
The influence of stress on the microstructural stability of the DD10 single crystal superalloy was investigated using SEM after long-term aging at 1100℃ and stress rupture testing at 1100℃/140MPa. The results indicate that the TCP (topologically-close-packed) phases formed after aging at 1100℃ for 253h and stress-rupture at 1100℃/140MPa are μ phases enriched with Re, W, Cr and Mo. The stress promotes the formation of μ phase, and the amount of μ phase increases with the stress increasing at 1100℃/140MPa. However, stress does not influence the type and morphology of TCP phase. In addition, the stress accelerates the rafting process of γ'.
Ab Initio Study on Melt Structure of 55% Al-Zn Alloy
XING Wen-guo, MENG Xian-xing, FENG Wei-chun, ZHANG Chang-qiao
2014, 34(2): 6-10. doi: 10.3969/j.issn.1005-5053.2014.2.002
[Abstract](136) [PDF 1454KB](1)
The first-principle molecular dynamics simulation was employed to study the melt structure of 55% Al-Zn alloy using Vienna ab initio simulation package (VASP). The structure and dynamic properties of the melt were obtained. The results indicate that the calculation value of structure factor is in agreement with the experimental value. The atomic distribution of Al does not apparently change after adding Zn atom. The ratio between the coordination number of Al-Al and Al-Zn in Al-Zn alloy melt is about 3:1,which is coincident with the ratio of the atom content in alloy melt. The Zn atom distributes randomly and homogeneously. The effects of cage Al forms from nearest-neighbor atom on impeding motion were intensive.
Influence of Bath Composition on Microstructure and Mechanical Properties of Electroformed Nickel
QIAN Jian-gang, LI Peng-rui, LI Hai-ting
2014, 34(2): 11-16. doi: 10.3969/j.issn.1005-5053.2014.2.003
[Abstract](157) [PDF 2052KB](2)
Nickel layer was successfully electroformed in sulphamate solution. The influence of bath composition on the microstructure, internal stress and tensile properties of electroformed nickel were studied by optical microscope, thin film flexural method and universal testing machine, respectively. The results show that, with the increase of the amount of nickel sulphamate, the gain size of the electroformed nickel increases, the internal stress and tensile strength decrease, but elongation increases correspondingly. As the content of nickel chloride increases, the gain size of the electroformed nickel becomes coarse and then refined, and the internal stress increases. Besides, tensile strength decreases before increases, and elongation decreases correspondingly. When the compositions of nickel sulphamate and nickel chloride are 300g/L and 3g/L, respectively, the comprehensive properties of nickel layer are good. And the internal stress, tensile strength and elongation are 60.7MPa, 811.7MPa and 23.5% respectively.
Influence of Current Type on Microstructure and Property of Sulfamate Type Electroforming Ni-Co Alloy
PEI He-zhong, LI Xue, HUANG Pan, LU Feng, ZHANG Jun, ZHANG Guo-liang
2014, 34(2): 17-21. doi: 10.3969/j.issn.1005-5053.2014.2.004
[Abstract](142) [PDF 2159KB](1)
The Ni-Co alloy electroforming layer was prepared by pulse current and DC current. The influences of pulse current and DC current on cast layer's microhardness,cobalt content,surface morphology and microstructure were obtained and analyzed by microhardness measurement device,EDS SEM and X-ray diffraction. The results show that the microhardness of casting layers are high either by pulse current or by DC, and it decreases with the increase of Dk. The microhardness of casting layer which was made by pulse current declines more slowly than that made by DC current. With the increasing of Dk, the cobalt content of nickel-cobalt alloy electroforming layer decreases, and decreases more slowly with pulse current increasing. The type of current has strong effect on cast layer's surface morphology. The cast layer crystal cell made by pulse current is uniform and seems cauliflower. The cast layer grain distribution made by DC current is uneven and blocky. Compared with direct current, pulsed current has slightly effect on the microstructure of the cast layer.
Influence of Aging Treatment on Microstructure and Corrosion Behavior of 2124 Aluminum Alloy Pre-Stretching Plate
NIE Hui-wen, PAN Qing-lin, NIE Jun-hong
2014, 34(2): 22-28. doi: 10.3969/j.issn.1005-5053.2014.2.005
[Abstract](145) [PDF 2897KB](1)
The microstructures and corrosion properties of 2124 aluminum alloy pre-stretching plates after aging were investigated using transmission electron microscopy (TEM), intergranular corrosion, exfoliation corrosion and polarization curve tests. The influence of aging treatment on corrosion resistances was analyzed. The results show that, with the increase of aging temperature or aging time, interior precipitates chang from S' phase to S phase. The amount and size of precipitates both increase. After aging at high temperature or for long time, the grain boundary precipitates present chain distribution and become coarser. Moreover, wide precipitate-free zones appear near the grain boundary. Intergranular and exfoliation corrosion resistances decrease and corrosion sensitivity increases with the increase of aging temperature or aging time. With the increase of aging temperature or aging time, alloy is susceptible to corrosion, and its corrosion rate also increases. The effect of aging treatment on corrosion sensitivity is closely related to S' phase, the phase precipitated in grain boundary and precipitate-free zone.
Generation Mechanism of Oxygen Rich α Layer in TA15 and TA2 Titanium Alloy
YU Hao, ZHANG Xiao-qing, WU Rui, LIU Yong, HOU Li-hua, ZHOU Yi, SONG Ti-jie
2014, 34(2): 29-34. doi: 10.3969/j.issn.1005-5053.2014.2.006
[Abstract](219) [PDF 5356KB](1)
The oxygen-rich α layers in TA2 and TA15 alloy after various heat treatments were studied. The forming thermodynamics and kinetics of oxygen-rich α layer were discussed. Optical microscope was used to observe α layer and measure its thickness. The results show that both heat treatment temperatures and holding times control the forming of oxygen-rich α layer, and temperature is main factor. The kinetics curves of α layer controlled by oxygen diffusion show parabolic shape. The thermal activation energy calculated results of α layer are 146.48 kJ/mol of TA15 alloy and 59.97kJ/mol for TA2 alloy. The alloy type and alloying elements, delaying diffusion of oxygen in the α phase, is the main reason of the difference between these two alloys. A three-dimensional curve of TA15 alloy was created to show the layer thickness under different conditions of exposure temperature and time.
Influence of Stirring Tool Material on Temperature Fields of Friction Stir Welding
ZHAO Yang-yang, LI Jing-yong, LI Xing-xue
2014, 34(2): 35-39. doi: 10.3969/j.issn.1005-5053.2014.2.007
[Abstract](188) [PDF 12613KB](1)
The temperatures in welding workpieces and stirring tools were measured, and the effect of material on the temperature fields of friction stir welding was investigated. The results indicate that the temperature distributions in welding workpieces and stirring tools have the same trends for different tool materials, the temperature and its gradient reduce gradually with the temperature measurement points far away from the weld center in the workpieces and from the shoulders in the stirring tools. The peak temperature in the workpieces rises gradually along with the welding direction, and the temperature at the advancing side is higher than that in the retreated side. The temperature fluctuation in stirring tools are very small at the stable welding stage because of equilibrium between the heat quantity produced by friction between stirring tool and workpiece and that dissipated through the stirring tool. The temperature in the workpieces and stirring tools is higher while a stirring tool made of material with smaller specific heat capacity and larger thermal conductivity is used as it produce more heat to friction pairs, but lead to more heat dissipation through it.
Influence of Polarization Potential on Stress Corrosion Cracking Susceptibility and Film-Induced Stress of 7050 Aluminum Alloy
QI Xing, SONG Ren-guo, QI Wen-juan, JIN Ji-rong, WANG Chao, LI Hai, XIONG Ying
2014, 34(2): 40-45. doi: 10.3969/j.issn.1005-5053.2014.2.008
[Abstract](143) [PDF 2198KB](1)
A passive film-induced tensile stress formed at the surface of 7050 aluminum alloy during corrosion in a 3.5% NaCl solution (pH=10) at different potentials was measured by flowing stress difference method. Simultaneously, the susceptibility to stress corrosion cracking (SCC) of alloy in 3.5% NaCl solution at various applied potentials was measured using slow strain rate testing (SSRT). The results show that a tensile stress is generated by the passive film during original corrosion. The passive film-induced tensile stress increases steeply with increase in potential under anodic potential. When the cathodic potential E≥-1100mV, the film-induced tensile stress decreases with increase in potential. Correspondingly, the film-induced tensile stress increases. The variation of film-induced stress with potential is consistent with that of susceptibility to SCC with potential.
Preparation and Properties of MWNT/PEK-C Electrical Conductive Film
HEI Yan-wei, ZHANG Bao-yan, ZHOU Zheng-gang, XU Xin-guang
2014, 34(2): 46-50. doi: 10.3969/j.issn.1005-5053.2014.2.009
[Abstract](172) [PDF 2088KB](1)
A kind of multi-walled carbon nanotubes (MWNT)/PEK-C composite film was prepared using WD-01 dispersing agent assistant ball-milling dispersion method and immersion coating technology. The effects of resin concentration, ball-milling time, coating solution storage time and MWNT content on the electrical conductivity of the film were analyzed, and the influences of carbon nanotubes and residual solvent on the thermal mechanical performance of the film were investigated. The results show that the MWNT is sheared and effectively dispersed using WD-01 dispersing agent assisting ball-milling dispersion method. Coating solution with higher viscosity effectively restrains the re-agglomeration of MWNT. Electrical conductivity of the film increases linearly with the increase of MWNT content from 8% to 33.3% (mass fraction). When carbon nanotubes content is 33.3%, the electrical conductivity of the film reachs up to 7.2S/cm. Carbon nanotubes adsorbing solvent conduces the decrease of glass transition temperature (Tg) of the film.
Scarf Repair Process of Composite Honeycomb Sandwich Structure by Hot Bonder
SUN Kai, YAN Dong-xiu, KONG Jiao-yue, WEI Ran, LIU Wei-ping
2014, 34(2): 51-57. doi: 10.3969/j.issn.1005-5053.2014.2.010
[Abstract](238) [PDF 3675KB](2)
Scarf repair process of composite honeycomb sandwich structure was conducted by hot bonder. The in-plane and through-thickness direction temperature distribution of composite honeycomb sandwich structure repaired by hot bonder was tested with thermocouples. The internal quality of HTS/977-2 and HTS/MTM44-1 plates with various repair layers cured by hot bonder was analyzed with optical microscope. Meanwhile, the edgewise compressive strength and bending strength recovery properties of honeycomb sandwich structure specimens with different damage types were studied before and after repair. The results indicate that temperature unevenness exists in through-thickness direction of honeycomb sandwich when applying hot bonder to repair. Multi-stage repair can be adopted confronting with one side panel and core damage or penetrate damage. Also the results reveal that there is restriction on the repair plies while adopting hot bonder. The maximum cured plies limits vary with the characteristic of the repair material. Hot bonder repair with four or five plies each time for HTS/977-2, while it is over ten plies for HTS/MTM44-1, the best performance is achieved. After the hot bonder repair, the recovery rate of specimen edgewise compressive strength is over 79.9%, and that of specimen bending strength is over 89.4%. The results verify the feasibility of scarf repair process by hot bonder for composite honeycomb sandwich structure.
Dynamic Mechanical Properties of Damping Silicon Rubber/Styrene-Butadiene Rubber Blend
TU Chun-chao, WANG Shan, REN Yu-zhu, JIANG Hong-gang, HUANG Yan-hua
2014, 34(2): 58-62. doi: 10.3969/j.issn.1005-5053.2014.2.011
[Abstract](194) [PDF 1375KB](1)
SE2045/SBR rubber compound was prepared by blending silicone rubber SE2045 and SBR by heat-kneading method. The effects of temperature,frequency and strain on properties of the rubber compound were investigated by using RPA 2000.The results show that, compared with SE2045, 10% addition of SBR improves the tensile strength of the rubber compound to 10.58MPa, which increases by 28.4%, and improves the tear strength to 51.6 kN/m, which increases by 260%. The addition of SBR also enhanced damping and modulus properties, but brought down the processing behaviors of the rubber compound. The changing tendency of properties with temperature and frequency remain the same. However, as the strain vary from 1% to 20%, the tanδ of SE2045/SBR rubber compound decreases firstly and then increases, while the silicone rubber SE2045 declines at the beginning and then reaches the stable status.
Preparation and Performance of High Temperature Heat-Resistant Organic Adhesive for Joining Al2O3 Ceramics
QIN Yan, RAO Zhi-long, HUANG Zhi-xiong
2014, 34(2): 63-68. doi: 10.3969/j.issn.1005-5053.2014.2.012
[Abstract](151) [PDF 2152KB](2)
High-temperature organic adhesive was prepared using preceramic polysiloxane as matrix, TiB2 powder and low melting point glass powder as additives. The curing mechanism, thermal properties, pyrolysis products of the phase composition, microstructure and the bonding mechanism of adhesive were investigated using FTIR, TGA, XRD, SEM, and bonding strength tests. The results show that the adhesive is cured through polycondensation reaction. The incorporation of TiB2 ceramic powder and glass powder induce chemical reaction with pyrolysis products derived from preceramic polysiloxane, which was the important reason that adhesive had exhibited outstanding heat-resistant properties and high bonding strength at high temperature.
Influence of Carbon Fiber Heat Treatment on Fracture Toughness of 2D C/C-SiC Composites
DAI Ji-xiang, SHA Jian-jun, ZHANG Zhao-fu, LI Jian, WEI Zhi-qiang
2014, 34(2): 69-76. doi: 10.3969/j.issn.1005-5053.2014.2.013
[Abstract](146) [PDF 2970KB](4)
In order to investigate the influence of carbon fiber heat treatment on the fracture toughness of 2D C/C-SiC composites via liquid silicon infiltration process, the carbon fiber was heat-treated at temperatures range from 600℃ to 1500℃ under vacuum. The fracture toughness was evaluated using single edge notched beam (SENB) test. The surface morphologies of C/C preform, C/C-SiC composites and the fracture surface were observed using scanning electron microscopy (SEM). The porosity and density were measured using the Archimedes method. The results indicate that the fracture toughness increases with increasing the heat treatment temperature of carbon fiber. The fracture toughness of composite reinforced with the 1200℃ heat-treated fiber is about 7.9MPa·m1/2, which is increases by 53% in comparison to that of the untreated fiber reinforced composite. The results of SENB test and structure show that the high fracture toughness in heat treated fiber reinforced composite is attributed to the strong fiber/matrix bonding strength, homogeneous distribution of SiC and high volume fraction of SiC in matrix.
Shape Parameter in Detail Fatigue Rating
GUO Xiang, LIU Jian-zhong, HU Ben-run, HUANG Xiao
2014, 34(2): 77-83. doi: 10.3969/j.issn.1005-5053.2014.2.014
[Abstract](201) [PDF 843KB](1)
In order to obtain more accurate and reliable DFR value, two-ordered statistic (TOS) method is introduced and verified. An assessment for TOS and common estimators is made by Monte Carlo simulation, and TOS method is used for analyzing a large amount of measured data. Systematical parameter estimation and analysis are taken for aviation materials including steel, aluminum and titanium. A further analysis is taken for factors which may affect scatter in fatigue life. As a result, TOS has high accuracy in calculating α. Value life range has an obvious impact on domestic aviation materials'α. Ultimate strength and corrosive environments have impact on several materials. Recommended α values for common domestic material are in the range of 4.85-6.71. And new α estimated values of new aviation material aluminum lithium alloy, fiber metal laminates under the corrosive environment is given out.
Probabilistic Method to Predict Fatigue Life Based on Crack Initiating Micro-Mechanism of Aluminum Alloy
TAN Xiao-ming, ZHANG Dan-feng, CHEN Yue-liang, JIN Ping
2014, 34(2): 84-89. doi: 10.3969/j.issn.1005-5053.2014.2.015
[Abstract](183) [PDF 2350KB](4)
Using scanning electron microscope (SEM), the morphology of fatigue fracture of 2B06 aluminum sheet specimen was investigated, and the micro-mechanism of fatigue crack initiation was evaluated. Using optical microscope, the size of the second phase particles was measured, and the best distribution rule and fitting probability distribution functions were obtained using statistical analysis. A probabilistic approach to predicting fatigue life based on crack initiating micro-mechanism was put forward in accordance with the probabilistic fracture mechanism. The fatigue life for different reliability (90%, 95%, 99% and 99.9%) was calculated. By comparison between testing fatigue life and calculation, the theoretical model was validated. The results show that the probabilistic method can simulate the variability of fatigue life, and it is feasible and reasonable.
Effect of Biaxial Pre-Stretching on Residual Stress of New Quenching State Aluminum Alloy 2024 Thin Plates
GUO Rui-chao, WU Jian-jun, ZHANG Shen, LI Hao
2014, 34(2): 90-97. doi: 10.3969/j.issn.1005-5053.2014.2.016
[Abstract](142) [PDF 3147KB](1)
Local shallow stretch forming experiment was used to simulate biaxial pre-stretching. Based on ABAQUS finite element software, biaxial pre-stretching model was established, The influence of the stress ratio and principal pre-stretching quantity on residual stress were analyzed and the simulate relative optimized parameters of the biaxial pre-stretching were obtained. Through plane strain test, experimental parameters were achieved. In order to verify the reliability of the FEA, ARAMIS was used to measure strain and X-ray diffractometer was used to get the residual stress. The results show that the residual stress is minimum when the pre-stretching amount is 2.0% and the stress ratio is 0.45.

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