2017 Vol.37(1)

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2017-01-Catalog
2017, 37(1): 0-0.
[Abstract](80) [PDF 1108KB](2)
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Integrated Computing Materials Engineering Column
Integrated Computational Materials Engineering (ICME) for Developing Aluminum Alloys
Yong DU, Kai LI, Pizhi ZHAO, Mingjun YANG, Kaiming CHENG, Ming WEI, Yi KONG, Siliang LIU, Huixia XU, Na TA, Kai XU, Fan ZHANG, Han LI, Zhanpeng JIN
2017, 37(1): 1-17. doi: 10.11868/j.issn.100-5053.2016.100004
[Abstract](191) [FullText HTML] (119) [PDF 7744KB](16)
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The ICME (Integrated Computational Materials Engineering) for aluminum alloys was applied to combine key experiments with multi-scale numerical simulations from nano (10-10-10-8 m) to micro (10-8-10-4 m) to meso (10-4-10-2 m) and to macro (10-2-10 m) during the whole R & D (research and development) process of aluminum alloys. Using integrated analysis of the composition-processing-structure-properties, the methodology for developing aluminum alloys was promoted from trial and error to scientific design, SO the R & D of aluminum alloys was significantly speed up and the cost was reduced. In this paper, multi-scale simulation approaches including Ab-initio, CALPHAD (CALculation of PHAse Diagram), phase field, and finite element method together with experimental methods characterizing structure and properties are elaborated. The function of each method in the R & D of aluminum alloys is carefully discussed. Based on ICME, the framework for R & D of aluminum alloys, involving end-user demand, product design and industrial design, is established. Two application examples are presented to describe the important role of ICME during the development stage of aluminum alloys, which provides an innovative pattern for R & D of advanced aluminum alloys.
Strengthening and Toughening Design and Development of Mg-Rare Earth Alloys
Xiaoqin ZENG, Xiaoying SHI
2017, 37(1): 18-25. doi: 10.11868/j.issn.1005-5053.2016.100001
[Abstract](324) [FullText HTML] (86) [PDF 13578KB](7)
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Magnesium alloys are the lightest structural alloys developed so far and have a great potential for lightweight applications, ranging from portable electronic devices to automobile parts. Comparing to Mg alloys containing no rare earth (RE), Mg-RE alloys attracted more and more attentions due to the higher strengths at both room temperature and elevated temperature. Strengthening methods for Mg alloys with high RE contents and low RE contents were introduced respectively in this paper. For Mg alloys with high RE contents, precipitates of β' lying in the triangular prismatic plates can impede dislocation slip effectively to enhance the strength of the alloy. For Mg alloys with low RE contents, the microstructure containing nano grains in the surface layer and twinning in the center can be obtained by surface mechanical attrition treatment. Thus the Mg alloy can be strengthened by both refinement strengthening of nano grains and twinning strengthening of RE segregated twin boundaries.
MGI-oriented High-throughput Measurement of Interdiffusion Coefficient Matrices in Ni-based Superalloys
Ying TANG, Juan CHEN, Yong DU, Lijun ZHANG
2017, 37(1): 26-35. doi: 10.11868/j.issn.1005-5053.2016.100003
[Abstract](357) [FullText HTML] (70) [PDF 8031KB](14)
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One of the research hotspots in the field of high-temperature alloys was to search the substitutional elements for Re in order to prepare the single-crystal Ni-based superalloys with less or even no Re addition. To find the elements with similar or even lower diffusion coefficients in comparison with that of Re was one of the effective strategies. In multicomponent alloys, the interdiffusivity matrix were used to comprehensively characterize the diffusion ability of any alloying elements. Therefore, accurate determination of the composition-dependant and temperature-dependent interdiffusivities matrices of different elements in γ and γ' phases of Ni-based superalloys was high priority. The paper briefly introduces of the status of the interdiffusivity matrices determination in Ni-based superalloys, and the methods for determining the interdiffusivities in multicomponent alloys, including the traditional Matano-Kirkaldy method and recently proposed numerical inverse method. Because the traditional Matano-Kirkaldy method is of low efficiency, the experimental reports on interdiffusivity matrices in ternary and higher order sub-systems of the Ni-based superalloys were very scarce in the literature. While the numerical inverse method newly proposed in our research group based on Fick's second law can be utilized for high-throughput measurement of accurate interdiffusivity matrices in alloys with any number of components. After that, the successful application of the numerical inverse method in the high-throughput measurement of interdiffusivity matrices in alloys is demonstrated in fcc (γ) phase of the ternary Ni-Al-Ta system. Moreover, the validation of the resulting composition-dependant and temperature-dependent interdiffusivity matrices is also comprehensively made. Then, this paper summarizes the recent progress in the measurement of interdiffusivity matrices in γ and γ' phases of a series of core ternary Ni-based superalloys achieved in our research group. Up to now, the interdiffusivity matrices in γ and γ' phases of the core ternary systems including Ni-Al-X (X=Rh, Ta, W, Re, Os and Ir) have been efficiently measured, and their reliability has also been carefully validated. Based on the experimental results, the interdiffusivities for different elements in Ni-based superalloys are carefully compared, from which the potential substitutional alloying elements for Re in Ni-based supperalloys as well as the points for alloy composition design are proposed. Finally, the research work of next step on the measurement of interdiffusivity matrices in Ni-based superalloys as well as the development trends of high-throughput measurement of interdiffusivities in our research group are pointed out.
Experimental Characterization of Ultrastructure of Aviation Aluminum Alloys
Mingjun YANG, Kai LI, Yong DU, Jiong WANG, Siliang LIU, Yi KONG
2017, 37(1): 36-51. doi: 10.11868/j.issn.1005-5053.2016.100002
[Abstract](311) [FullText HTML] (77) [PDF 49197KB](7)
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In order to improve the comprehensive performance of aluminium alloys for the aviation application, it is necessary to experimentally characterize the microstructure, and thus to build a bridge between the microstructure and macro-performance of aluminum alloys. This paper introduces the brief developing course of 2xxx, 6xxx and 7xxx aluminum alloys and their microstructure evolution during artificial aging.The structural characteristics of significant phases like GP zones in Al-Cu alloys and GPB zones in Al-Cu-Mg alloys, and the precipitation behavior of S phase in Al-Cu-Mg alloys, etc, are thoroughly studied. The application of Transmission Electron Microscopy, Scanning-Transmission Electron Microscopy, 3-Dimentional Atom Probe in the investigations of structure, morphology, composition, interface structures, intergranular corrosion resistance and so on has been reviewed, especially the Ω phase in Al-Cu-Mg-Ag alloys and β" phase in Al-Mg-Si-Cu alloys. Our group has finished the works such as the simulation and characterization of complex selected area electron diffraction patterns in Al alloys, as well as the measuring of the precipitates' volume fraction with high accuracy which is based on the convergent beam electron diffraction.
Research Paper
Influence of Processing Speed on Microstructure and Mechanical Properties of ZK60 Magnesium Alloy Prepared by Friction Stir Processing
Jun LIN, Datong ZHANG, Wen ZHANG, Cheng QIU
2017, 37(1): 52-58. doi: 10.11868/j.issn.1005-5053.2016.000116
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ZK60 casting magnesium alloy was subjected to friction stir processing (FSP). Defect-free joints could be obtained under a range of processing speeds (50-200 mm/min) at a constant rotation rate of 800 r/min, and microstructures and mechanical properties of the experimental materials were investigated. The results show that the coarse grains in base material are changed into fine equiaxed grains in stir zone after FSP. With the increas of processing speed, the mean grain size decreases firstly and then increases. The microhardness and tensile strength of stir zone increase compared with the base material, and the elongation increases significantly due to its fine and uniform microstructure of the specimen. The optimum properties are obtained in the specimen prepared at the processing speed of 100 mm/min, the average grain size of the specimen is 6.9 μm, and the microhardness, tensile strength and elongation are 70.1HV, 276 MPa and 31.6% respectively.
Corrosion Behavior of 7B04 Al-alloy in Simulated Marine Atmospheric Environment
Chenguang WANG, Yueliang CHEN, Yong ZHANG, Guixue BIAN
2017, 37(1): 59-64. doi: 10.11868/j.issn.1005-5053.2016.000120
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The corrosion of aluminum alloy in marine atmospheric environment was an essential electrochemical corrosion under thin electrolyte film, which was different from the corrosion in bulk solution, the corrosion rate was related to the thickness and composition of thin electrolyte film. The relationship among film thickness, relative humidity and salt deposit on aluminum alloy surface was established and verified by experiment. The electrochemical properties of 7B04 Al-alloy under thin electrolyte film with different thickness and different NaCl concentration were studied. The results indicate that the free-corrosion potential of 7B04 Al-alloy under thin electrolyte film is easier to reach steady state than that in bulk solution, both free-corrosion potential and corrosion rate are higher under thin electrolyte film. With the decrease of film thickness, the cathodic polarization current density of 7B04 Al-alloy increases, and the anode reaction is suppressed. With the increase of NaCl concentration in thin electrolyte film, the free-corrosion potential of 7B04 Al-alloy decreases, and the corrosion rate increases, but the polarization of the anode and cathode have little effect on the change of NaCl concentration. The free-corrosion potential of 7B04 Al-alloy is no longer changed when the mass fraction of NaCl reaches 5%.
Contrasty Tests on Fatigue Properties of Aluminum Alloys 2E12-T3 and 7050-T7451 in Pooding Environment of Fuel Tank
Kuang LI, Junjiang XIONG, Shaojun MA, Bo CHEN
2017, 37(1): 65-72. doi: 10.11868/j.issn.1005-5053.2016.000093
[Abstract](232) [FullText HTML] (61) [PDF 38038KB](2)
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Fatigue properties in typical corrosion environments are the premise of fatigue life design for metallic structures in aircraft. Therefore, fatigue tests were performed on smooth and notched specimens subjected to constant amplitude loading in two environments of dry air and fuel tank ponding respectively to determine pure and corrosion fatigue properties of aluminum alloys 2E12-T3 and 7050-T7451. Corrosion fatigue properties in the two environments were analyzed and compared with each other, and the interaction mechanisms between corrosion and fatigue were deduced from fractographical studies by using scanning election microscope (SEM). It is showed that fuel tank ponding has a detrimental influence on fatigue properties and the adverse effect increases with the decreasing stress level. In addition, the notch of specimen enhances the severity of corrosion effects. Fatigue crack is easily initiate from the corrosion pits on the rough fatigue surface, and crack propagation is enhanced by the corrosion products and the hydrogen embrittlement effects at crack tips, thus the degradation of fatigue properties and the reduction of fatigue life are caused.
Simulation of Effect of Twin boundary on Mechanical Property of α-Fe
Tianhan XU, Song HE
2017, 37(1): 73-79. doi: 10.11868/j.issn.1005-5053.2016.000134
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The effects of twin boundary spacing and angle between loading axis and twin boundary on the mechanical behavior of nano-twinned Fe under the uniaxial tensile load were studied by molecular dynamic simulation. The results indicate that the yield stress of nano-twinned Fe increases with the increase of twin boundary spacing, showing a trend of inverse Hall-Petch relation. The deformation twin exhibits in the single crystal iron, which is predominant in the plastic deformation process. The elastic modulus of nano-twinned Fe increases slightly with the increase of twin boundary spacing. When the tensile load is not perpendicular to the twin boundary, the yield stress decreases and the deformation is mainly detwinning.
C/C-SiC Composites for Nozzle of Solid Propellant Ramjet
Lingling WANG, Alin JI, Yaqi GAO, Hong CUI, Liansheng YAN, Fei PANG
2017, 37(1): 80-85. doi: 10.11868/j.issn.1005-5053.2015.000214
[Abstract](289) [FullText HTML] (76) [PDF 10874KB](7)
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Carbon fiber reinforced carbon and silicon carbide matrix composites for nozzle inner of solid propellant ramjet were prepared by using the hybrid process of "chemical vapor infiltration + precursor impregnation pyrolysis (CVI+PIP)". The microstructure, flexural and anti-ablation properties of the C/C-SiC composites and hydraulic test and rocket motor hot firing test for nozzle inner of solid propellant ramjet were comprehensively investigated. The results show that when the flexural strength of the composite reachs 197 MPa, the fracture damage behavior of the composites presents typical toughness mode.Also the composites has excellent anti-ablative property, i.e., linear ablation rate is only 0.0063 mm·s-1 after 200 s ablation. The C/C-SiC component have excellent integral bearing performance with the hydraulic bursting pressure of 6.5 MPa, and the high temperature combination property of the C/C-SiC composite nozzle inner is verified through motor hot firing of solid propellant ramjet.
Basic Formability Research and Experimental Test of Glass Fiber Reinforced Aluminium Laminates
Jingming TIAN, Huaguan LI, Cheng LIU, Gang TAO, Liqing ZHANG, Xingwei ZHENG, Hongbing LIU, Jie TAO
2017, 37(1): 86-92. doi: 10.11868/j.issn.1005-5053.2015.000213
[Abstract](245) [FullText HTML] (65) [PDF 10074KB](5)
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The basic formability of Glare 2A, Glare 2B and Glare 3 laminates was investigated by unidirectional tensile and three-point bending tests to explore the formability characteristics of Glare. Meanwhile, the failure characteristic of Glare was studied by scanning electron microscopy (SEM). The results indicate that the direction of the fiber has strong effects on the formability of Glare. The Glare 2A laminates exhibit the strongest resistance to plastic deformation. Meanwhile, it is also hard to deform in thickness direction.σ=σy+n is used to fit the real stress-strain curves of three variants and proves the most suitable model, presenting the maximum correlation coefficient. Furthermore, Glare 2A laminates exhibit the most serious bending springback. Shrinkage and compression fracture are visible in the inner layer which bears compressive stress, and fiber fracture and delamination are found in the outer layer which bears tensile stress. On the contrary, Glare 2B laminates show the minimum springback, following with the observed fiber-matrix cracks. Finally, the accuracy of test results is verified by roll bending.
Degradation Mechanisms of Transparent Polyurethane Interlayer under UV Irradiation
Yingchun OU, Xiaona MA, Yanfang ZHANG, Jing FU, Ruixiang QIN, Juanrong MA
2017, 37(1): 93-98. doi: 10.11868/j.issn.1005-5053.2016.000031
[Abstract](323) [FullText HTML] (70) [PDF 7895KB](8)
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According to the ageing problem of laminated transparency, the trasparent polyurethane film used as interlayer had been irradiated by fluorescent ultraviolet lamp for 0 h, 200 h, 300 h, and 500 h respectively. With the aid of ultraviolet/visible spectrophotometer, FTIR and SEM etc., the color, structure and morphology of the materials were studied. SEM shows that when the irradiation time is increased to 500 h, the film surface cracks. The UV degradation mechanisms are that -CH2-of the position connecting the O and N from hard segment and the soft segment are easy to oxidize and produce hydrogen peroxide under UV and oxygen, which is furtherly oxidized to CO, and some part of the C-O and C-N bonds is cracked through β scission, and then the materials are fractured.
Comparison of Composites Properties Manufactured by Vacuum Process and Autoclave Process
Rufei MA, Jiajun GUI, Jiajun GUO, Fenghui SHI, Baoyan ZHANG
2017, 37(1): 99-103. doi: 10.11868/j.issn.1005-5053.2015.000206
[Abstract](261) [FullText HTML] (66) [PDF 3912KB](7)
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Two kinds of prepregs ZT7G/LT-03A (unidirectional carbon fiber prepreg) and ZT7G3198P/LT-03A (plain carbon fabric prepreg) were used to manufacture three Bateches of composites by vacuum process and autoclave process respectively. The physical properties of the prepregs and mechanical properties of composite were tested. The performance, fiber volume content and porosity of composites manufactured by vacuum cure and autoclave process show that the physical property retention rates of vacuum cured composites are all over 75%, some even more than 100%. Interlaminar shear strength keeps the lowest retention rate and warp tensile strength keeps the highest retention in unidirectional carbon fiber composites. For fabric composite material, compression strength keeps the lowest and warp tensile strength keeps the highest retention. Vacuum cured composites perform lower fiber volume content and higher porosity, which are the main reasons of the lower performance.
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