2015 Vol.35(3)

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2015, 35(3): 0-0.
[Abstract](88) [PDF 9111KB](2)
Impact of Texture and Microstructure on In-plane Anisotropy of Ultra-high Strength Aluminium Alloy
Zhi-feng MA, Wei-yi ZHAO, Zheng LU
2015, 35(3): 1-6. doi: 10.11868/j.issn.1005-5053.2015.3.001
[Abstract](293) [FullText HTML] (59) [PDF 1935KB](3)
In order to master the impact of texture and microstructure on the in-plane anisotropy of tensile mechanical properties of ultra-high strength Al-Zn-Mg-Cu alloy,the extruded plate and its isothermal forged piece were manufactured. The microstructure, tensile mechanical properties and the intensity of texture were tested and the Schmidt factors were calculated. The relationship of the texture, microstructure and the tensile strength anisotropy were observed by means of single crystal model with Schmidt factor and Hall-Petch law. The results show that the alloy is dominated by deformation texture after intense deformation, and deformation textures leads lower strength of 45° and causes anisotropies. Fibrous tissue formed by extrusion is the main reason of the anisotropy in L and LT directions. The increased strength caused by {110} <112>Brass texture can counterbalance the anisotropy in L and LT directions caused by fibrous tissue. The chainlike distribution of the second phase particles in grain boundary is the key factor of lower elongation of LT and the elongation anisotropy, also it is relevant to the grain strength changes caused by textures.
Effect of Solution Treatment Temperature on Microstructural Evolution of Ti2AlNb-based Alloy
Bin WANG, Kai-feng ZHANG, Shao-song JIANG, Peng LIN, Wen-long ZHOU
2015, 35(3): 7-12. doi: 10.11868/j.issn.1005-5053.2015.3.002
[Abstract](222) [FullText HTML] (69) [PDF 2985KB](3)
Intermetallic alloys based on an ordered orthorhombic Ti2AlNb phase are considered as promising materials for aerospace applications. The mechanical properties of the Ti2AlNb-based intermetallic alloy with three phases of O, B2 and a2, are sensitive with the phases and microstructure. In the present work, phase transformation of Ti2AlNb-based alloy during solution treatment at elevated temperatures was investigated by using optical microstructure (OM), scanning electron microscope (SEM), and transmission electron microscope (TEM). The results indicated that the transformation from O to B2 phase occurred and the α2 phase gradually vanishes with increasing the solution treatment temperature. The solution treatment temperature determine the amounts of O, B2 and α2 phase and their final microstructural morphologies, and also determine the properties of the material.
Mechanical Property and Fracture Mechanism of Nanocrystalline Aluminum
Sha-sha LI, Jiong-li LI, Jun-zhou Chen, Sheng-qiang WANG, Yan-cai XIONG
2015, 35(3): 13-17. doi: 10.11868/j.issn.1005-5053.2015.3.003
[Abstract](221) [FullText HTML] (75) [PDF 1739KB](3)
In this study, four groups of different process es of Ato+Ext, Ato+HIP+Ext, Cryo+Ext and Cryo+HIP+Ext were set to prepare bulk nanocrystalline/ultrafine-grained Al, and the mechanical properties of the bulks were determined. Then, tensile stress was analysized,the fracture morphology and corresponding dislocation morphology were observed respectively by scanning electron microscopy (SEM). Finally, the deformation and fracture mechanism were discussed. The result showed that the sample made with as-milled powder had an excellent strength compared to sample made with atomized powder. The indication of work hardening had not been observed in all tensile stress strain curves of the four samples. The dislocation movement, which could been seen obviously in ultrafine-grained samples, appeared only in large grain(≥100nm) in nanocrystalline samples. The tensile specimen of the bulk prepared via Ato+HIP+Ext exhibited a transcrystalline fracture, while intergranular fracture was happened to the other specimens.
Flow Stress Behavior and Microstructure of 7150 Aluminum Alloy during Hot Deformation
Ye-qing ZHAO, Yan LI, Fa-yun LU, Xiu-fan CHEN, Jun-peng LI, Fu-an GUO
2015, 35(3): 18-23. doi: 10.11868/j.issn.1005-5053.2015.3.004
[Abstract](218) [FullText HTML] (59) [PDF 2773KB](3)
The flow stress behavior and the deformation microstructure of 7150 aluminum alloy during hot compression deformation were studied by thermal simulation test using Gleeble thermal simulation machine at temperature ranging from 300℃ to 450℃ and strain-rate from 0.01s-1 to 10s-1. The constitutive equation of the plastic deformation of 7150 alloy at elevated temperature was obtained by introducing Zener-Hollomon parameter. The experimental results indicate that the flow stress and peak stress increase with increasing strain rate, and decrease with increasing deformation temperature, which can be described by a constitutive equation in hyperbolic sine function, whose values of related parameters A,α, n and activation energy for hot deformation Q, are 4.161×1014 s-1, 0.01956 MPa-1, 5.14336 and 229.7531kJ/mol respectively. With increasing the temperature and decreasing the strain rate, the main soften mechanism of the 7150 alloy transforms from dynamic recovery to dynamic re-crystallization.
Comparison of Microstructure and Mechanical Properties for TA15 Titanium Alloy Large Forgings under Two Die-forging Equipments
Wei-hong WANG
2015, 35(3): 24-28. doi: 10.11868/j.issn.1005-5053.2015.3.005
[Abstract](268) [FullText HTML] (67) [PDF 4154KB](5)
800MN die-forging press and 1MJ die-forging hammer were employed on TA15 titanium alloy to produce large aerial forgings. Microstructure and mechanical properties of TA15 forgings under the two forging equipments were investigated and compared. Results show that the forgings under 800MN die-forging press have a preferable plastic flow. The 800MN die-forging press will cause lager deformation and lower strain rate during every heating. The forgings under 800MN die-forging press have more fine grain size after recrystallization compared with those under 1MJ die-forging hammer. It also had a higher percentage of primary alpha phase as well as more fine α precipitation under 800MN die-forging press. As a result, its tensile properties and impact toughness and fracture toughness of the forgings are higher than those under 1MJ forging. Furthermore, the costs and quality are more ideal under 800MN die-forging press because the strain and strain rate are more controllable and the forging times are less.
Effects of Friction Changing on Part Thickness in SPF of TC4 Alloy
Zong-ke SHAO, Dong-ping YIN, Xiong-yao DU, Chong ZHANG
2015, 35(3): 29-34. doi: 10.11868/j.issn.1005-5053.2015.3.006
[Abstract](223) [FullText HTML] (62) [PDF 5521KB](2)
In order to study the influence of the friction on the thickness distribution of part in superplastic forming, based on TC4 negative angle complex parts, the influence of low-die in single-direct SPF and up-die in direct-reverse SPF on thickness distribution was analyzed with MSC. and MARC. The influence of friction changing in different areas of up-die in direct-reverse SPF on the minimum thickness and the thickness distribution were analyzed with ANOVA and range analysis. The results show that the smaller of friction, the greater thinning of the negative wall thickness while the thickness of positive angle wall was opposite. In direct-reverse SPF, when the friction of low-die is fixed, as the friction coefficient of up-die increases, the minimum thickness of actual part increases accordingly. There are different effects on minimum thickness and thickness distribution as the friction in different areas of up-die in direct-reverse SPF changes. The thickness effect of the part is greater while the sheet contacts the die earlier.
Effects of Cr Content on Microstructure and Mechanical Properties of Ti5Mo5V3Al-xCr Alloys
Xue-fei CUI, Xu-jun MI, Song-xiao HUI, Yan-guang WEI, Zheng LUO, Hai-ming TAO
2015, 35(3): 35-42. doi: 10.11868/j.issn.1005-5053.2015.3.007
[Abstract](252) [FullText HTML] (51) [PDF 3482KB](3)
Different Cr contents of Ti5Mo5V3Al-xCr (x = 1.0, 3.0, 5.0, 7.0, 9.0) alloys were solution treated in β phase region (above the phase transition point 20℃) and α+β phase region (below the phase transition point 30℃). And then aging at the same temperature of 520℃. The mechanical properties results show that the aging strengthening capacity of alloys decreased with increasing Cr content. Scanning electron microscopic and X-ray diffraction were used to analyze the correlation between the micro factors (such as phase composition, phase content, phase size and phase morphology) and the macro mechanical properties in different heat treatment conditions. The results show that the aging strengthening mechanism of Ti5Mo5V3Al-xCr alloys is mainly caused by the precipitation of αs phase in the process of aging. The aging strengthening capacity of alloys is closely related to the number of αs phase and the size of αs phase. The precipitation mechanism of αs phase is mainly dominated by the content of Cr element in Ti5Mo5V3Al-xCr alloys.
Effect of Holding Time on Microstructure and Mechanical Properties of K452 Superalloy Brazed Joints
Hai-sheng ZHAO, Hui PAN, Xue-jun ZHANG, Yong-chao LIU
2015, 35(3): 43-48. doi: 10.11868/j.issn.1005-5053.2015.3.008
[Abstract](414) [FullText HTML] (63) [PDF 2434KB](4)
Vacuum brazing of K452 superalloy was performed with cobalt-base filler metal and nickel-base superalloy powder under brazing conditions of 1170℃/10min, 1170℃/60min and 1170℃/120min respectively. The microstructure of brazed joints was analyzed by using SEM and EDS, and the high-temperature mechanical properties were also studied. The results show that the sound joints with fine microstructure and rare pores are achieved under 1170℃/60min brazing procedure, due to the good quality of interface. The joints braze under 1170℃/120min show the highest mechanical properties because of better interface quality, the average 900℃ tensile strength of 400MPa and 900℃/100MPa stress-rupture life of 141h/55min. But there morepoles are presented, and many white particles of compound congregated and grow up between the nickel-base superalloy powder in the brazing seam.
Effects of Aging Treatments on Microstructure and Micro-hardness of 2219-T87 Welds
Di-yao SU, Su-jun WU, Hui-jin JIN
2015, 35(3): 49-54. doi: 10.11868/j.issn.1005-5053.2015.3.009
[Abstract](255) [FullText HTML] (39) [PDF 2315KB](3)
The effects of post-weld aging treatment on microstructure and micro-hardness of aluminum alloy grade 2219 welds are presented. The microstructure including the precipitates distribution and morphology was observed by transmission electron microscopy (TEM) and micro-hardness was measured to characterize the different micro-areas across the weld. The results show that different post-weld aging temperatures lead to variations in microstructure and micro-hardness across the weld. Full reversion area (RA) in the heat affected zone (HAZ)is the most sensitive to the aging process. Micro-hardness in this area shows obvious improvement when it is processed at low aging temperatures, and the maximum increase is achieved at 160℃. The micro-hardness in the weld metal (WM) remains relatively stable. The maximum increase is achieved at 210℃. The over-aged area (OA) shows a very limited increase in micro-hardness and the maximum value is obtained at 160℃. TEM observation revealed that the changes in micro-hardness of micro-areas across the weld are mainly related with the precipitate evolution during the aging process.
Friction Stir Lap Welding with Pinless FSW Tool for Cu-Ni Alloy and Low-carbon Steel
Shou-fa LIU, Jin-peng WANG, Song-lin WU
2015, 35(3): 55-59. doi: 10.11868/j.issn.1005-5053.2015.3.010
[Abstract](351) [FullText HTML] (44) [PDF 1686KB](2)
Cu-Ni alloy (C71000) and low-carbon steel (Q235) were joined by friction stir lap welding (FSLW) with pinless FSW tool with the help of nickel coating. The influence mechanism of the thickness of the nickel coating on the steel side on tension-shear strength of the weld was studied by means of tension-shear tests, SEM and EDS. Researches show that Ni coating could prevent Fe from oxidizing and reduce the micro-voids of the joint face of the weld. High interface temperature and contact pressure during the welding could promote diffusion of the Fe and Cu atom into the Ni coating through the interface and form seamless connection. Increasing the thickness of the nickel coating on the steel side could contribute to the improvement of the tension-shear strength of the weld. When the thickness of the Ni coating on Cu-Ni side and steel side reached 5μm and 20μm respectively, the maximum tension-shear strength of 295MPa was achieved, which was 2.76 times that of the weld without Ni coating and close to Cu-Ni alloy.
Full-range Uniaxial Constitutive Relationship up to Failure of Polymer PA66
Si-miao YU, Li-xun CAI, Guo-ming ZHAO
2015, 35(3): 60-68. doi: 10.11868/j.issn.1005-5053.2015.3.011
[Abstract](223) [FullText HTML] (76) [PDF 3762KB](2)
Polymers have been widely used in various structural engineering, and the importance of relevance to their fracture properties and full-range constitutive relationships up to failure is attached recently. The accurate full-range constitutive relationships up to failure are important for light structure design and safety assessment. Based on finite-element-analysis aided testing(FAT) method[1], the full-range uniaxial constitutive relationship of PA66 is investigated. Meanwhile, the strain distribution field on the surface of funnel-shaped specimen is tested by the DIC (Digital image correlation) optical measurement system. Comparing the testing results with the finite element simulating results by FAT, both of them are coincided well. So it is accurate for FAT to obtain the full-range uniaxial constitutive relationship of PA66. As results, for PA66, the parameters of Chaboche constitutive relationship model, critical breaking stress, critical breaking strain, stress triaxiality of polymer material PA66 are obtained, and also the fracture behavior of those specimens were discussed.
Flap Structural Composites VARI Fluid Process Molding Simulation Technology and Experiments Validation
Fei XIAO, Mao-chuan JIANG, Qiang LIU, Zhi-ping CHEN, Bo-ming ZHANG
2015, 35(3): 69-76. doi: 10.11868/j.issn.1005-5053.2015.3.012
[Abstract](256) [FullText HTML] (68) [PDF 3713KB](5)
In the process of composites fluid molding, the filling time and pressure of resin can be forecasted with using computer-aided simulation software, which can provide reference design for the real molding process of resin flow. The simulation of the resin flow had been carried out for flap structural composite by using PAM-RTM software. According to the Darcy's law, the formula of permeability was deduced when the resin flow along reinforce fiber. The permeability of carbon fiber and suture fiber was tested and revised respectively. The simulation of the resin flow was carried out by using several runner means. The final reasonable injection port and runner were chosen according to simulation results. The chosen means were verified by the process experims, also the structural component was tested by using ultrasonic nondestructive testing. The results show that the theoretical filling time is almost consistent with the filling time measured by the experiments. It is not found that the internal defect is existed in structural components. The resin filling is enough, to prove that the simulation is valid.
Equivalent Rigidity Design Research of Laminated Spherical Rubber-metal Elastomeric Bearing
Gao-sheng CHEN, Fu-ping LI, Yan YANG
2015, 35(3): 77-82. doi: 10.11868/j.issn.1005-5053.2015.3.013
[Abstract](227) [FullText HTML] (68) [PDF 1444KB](3)
The formulations of compression rigidity and torsion rigidity of laminated spherical rubber-metal elastomeric bearing were deduced by theoretical means, the designed means of equivalent compression rigidity and equivalent torsion rigidity were studied, for the equivalent rigidity plan and unequal rigidity plan, the theoretical results and finite element simulated results of compression rigidity and torsion rigidity are calculated and taken comparied respectively, the results show that the equivalent rigidity design can eliminate the rigidity difference between different rubber layer to a large extent, the theoretical calculated results of compression rigidity and torsion rigidity are basically identical with the simulated results in every rubber layer.
Torsional Low-cycle Fatigue of C250 Steel by Using Funnel Specimen
Xing-hua ZHAO, Li-xun CAI, Zhi-hua JIANG, Chen BAO
2015, 35(3): 83-88. doi: 10.11868/j.issn.1005-5053.2015.3.014
[Abstract](217) [FullText HTML] (56) [PDF 2277KB](3)
Load-displacement (P-V) curve has been obtained of funnel specimen based on cyclic uniaxial tension and compression experiment, Based on the test results and finite element analysis iterative method, the effective cyclic constitutive relationships of C250 steel have been obtained. By using these effective cyclic constitutive relationships, 3D finite element analyses of funnel specimen under torsion are used to reveal the transforming relationship between the torque and the shear stress at the root of funnel specimen, the relationship between the nominal torsional angle and the shear strain at the root of funnel specimen. On the basis of those analyzing method, the low cycle fatigue study under torsion has been achieved. A series of torsional fatigue tests on C250 steel at room temperature by using funnel specimens have been carried out, the low cycle fatigue behavior of C250 steel has been revealed, and the typical Manson-Coffin model is employed to predict the torsional fatigue life of C250 steel.

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