FU Changpu HAN Yong
,
L(?) Shuangyun AN Yunzheng Shaanxi Mechanical Engineering Institute
,
Xi'an
,
ChinaPAN Jingda DU Wenfeng Beijing Heavy Electric Machine Works
,
China associate professor
,
Department of Materials
,
Shaanxi Mechanical Engineering Institute
,
Xi'an 710048
,
China
金属学报(英文版)
Studies were made of the creep properties and structure change of steet 20Cr11MoVNbNB at 550-650℃.It is found that at 550℃ when creep stress>180 MPa there exists linear rela- tion with two different slopes β_1 and β-2 between transitional creep strain ε_β and creep time t~(1/3),and β_1(in initiol period)>β_2(in later period).The Creep rate of stable stage at 550℃ can be expressed by =Aσ exp(-Q_ /RT),where,n=4.7.A exp(-Q_ /RT)= 5.37×10~(-16).Apparent creep activation energy Q_ =430 kJ/mol at 550-650℃,which is much higher than the self-diffusion activation energy of atoms for matrix Fe.In creep process,as the creep stress and time increase,the total weight of precipitated phases and rela- tive weight of Cr,Mo and V increase,but those of Fe and Nb decrease in precipitated phases,
关键词:
20Cr11MoVNbNB
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null
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null
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null
,
null
Journal of Materials Science
The effect of liquid phase on densification in electric-discharge compaction (EDC) was explored in the present work. The temperature at contact area of particles in EDC was estimated from random packing model incorporated with electric current distributions. Consolidation of cemented carbide and tungsten heavy alloys was conducted under varying current densities. WC-11Co/Fe/WC-11Co sandwich powder compacts were designed to investigate the effect of liquid phase flow. It is found that the densification occurred only when liquid phase formed, and relative density increased with the increasing of liquid phase volume. In the case of WC-11Co powders, the faceted grain evolution occurred but the significant grain growth was hardly observed, which meant the densification was mainly induced by particle rearrangement. The depth of liquid penetration of Fe in WC-11Co/Fe/WC-11Co sandwich compact also agreed with that caused by particle rearrangement processing. The possible effects of electric current on densification were also discussed.
关键词:
powder;metal;consolidation;growth;field
严东旭
,
刘天伟
,
龙重
,
白彬
,
张鹏程
,
黄河
,
郎定木
,
王晓红
,
朱建国
材料保护
采用单一的表面改性技术难以提高贫铀钛合金(Du-Ti)的耐蚀性能.采用等离子体浸没离子注入技术依次在Du-Ti合金表面注入N和Ti,再利用非平衡脉冲磁控溅射技术制备多层Ti/,TiN,研究了膜层的形貌、结构及耐蚀性能.结果表明:膜层厚约3μm,呈柱状结构,致密,但存在一些微缺陷,膜基结合紧密;膜层出现面心立方结构的TiN和密排六方的Ti,在DU-Ti合金界面形成了少量的UO2,没有铀的氮化物;膜层耐蚀性能较基体得到较大提高;微观缺陷是TiN层局部片状脱落的主要原因,外层TiN出现片状脱落后.注入层和内层Ti/TiN多层膜仍能有效保护基体.
关键词:
等离子体浸没离子注入
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非平衡磁控溅射
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复合膜
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DU-Ti合金
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电化学腐蚀
,
耐蚀性
SONG Qiang
钢铁研究学报(英文版)
Prediction of the alkalinity is a difficult problem during the process of sintering .Whether the level of he alkalinity of it is successful or not direct relates to the quality of sinter.By now,there isn’t a very good method due to the high complexity ,high non-linear, strong coupling, high delay-time and etc.A grey support vector machine model was proposed on the basis of the models.The fluctuation of data sequence is weakened by the grey theory and the support vector machine is capable of processing non-linear adaptable information, and the grey support vector machine is a combination of those advantages. The results reveal, the alkalinity of sinter can be accurately predicted through this model by reference to small sample and information. It was concluded that the grey support vector machine model is effective with the advantages of high precision, less samples required and simple calculation.
关键词:
alkalinity of sinter;grey least support vector machine;prediction;the sintering process;grey model.
International Journal of Cast Metals Research
Macrosegregation in heavy steel ingots was studied through numerical and experimental studies of a 500 kg ingot. The numerical model used heat conduction coupled with thermal convection. Simulation results confirm that a small 500 kg ingot poured in a sand mould has a solidification time that is equal to that of a 10 000 kg industrial ingot cast in an iron mould. Accordingly, the sand moulded ingot exhibits more severe macrosegregation compared to the iron moulded ingot, indicating the possibility that a relatively small ingot in sand can simulate conditions in a much heavier steel ingot in a conventional iron mould. Experiment demonstrated that a 500 kg ingot exhibited all the types of macrosegregation, including A- and V-segregates and negative and positive segregation commonly found in a 65 000 kg steel ingot.
关键词:
Macrosegregation;Heavy steel ingot;Numerical simulation;solidification;segregation;convection
Zhenhua LI
,
Yanxiang LI
,
Huiyuan GENG
,
Jianjun CHEN
,
Chunyan ZHOU
,
Junfa CHEN
材料科学技术（英文）
Using an artificial intelligent instrument and a computer feedback control method, a new thermal simulation system is studied. Based on numerical simulation of casting solidification, a sample in the new system successfully simulated the solidification of heavy section ductile iron. The results show that the new thermal simulation system is accurate and reliable. Not only cooling curve but also graphite in the center of the thermal sample and the heavy section ductile iron is identical. Realization of accurate thermal simulation of solidification in heavy section ductile iron will be helpful for studying formation mechanism and controlling graphite degeneration in heavy section ductile iron.
关键词:
Thermal simulation
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null
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null
Z.J.Ding
,
K.Salma
,
Z.M.Zhang
金属学报(英文版)
The full energy distribution of backscattered electrons from the elastic peak down to the true-secondaty electron peak for heavy metals, Ta, W, Pt and Au, in Auger electron spectroscopy in the EN(E) mode has been studied with a Monte Carlo simulation method, which includes cascade-secondary-electron production. The simulation model is based on the use of a dielectric function for describing inelastic scattering and secondary excitation, and on the use of Mott cross sections for elastic scattering. A systematic comparison between the calculated and experimental spectra measured with a cylindrical mirror analyzer has been made for primary energies ranging from 1 to 5keV. Excellent agreement was obtained for these heavy metals on the backscattering background at primary energies in the keV region. A significant contribution of cascade secondary electrons to the measured spectra on the low-energy side was found.
关键词:
backscattered electrons
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null
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null
Applied Physics Letters
We have used laser diffraction methods to demonstrate that water-in-oil microemulsions and emulsions under an electric field present diffraction patterns and optical activity, which can be tuned by the external electric field. When the optical rotation angle increases with the electric field, the electric vector of incident polarized light rotates clockwise. It is thought that the spatial symmetry breaking of the distribution of the droplets and the charges induced by the applied electric field is the origin of the phenomena in the complex fluids. (C) 2004 American Institute of Physics.
关键词:
photonic crystal;microemulsion;localization;phase
International Journal of Non-Equilibrium Processing
The effect of electric current pulses (ECP) on grain size in castings is considered. The relationship between grain size and electric current density is revealed. Numerical calculation shows that an electric current density with a magnitude of 10(3) A/cm(2) is needed to reduce the grain size by one order of magnitude for some pure metals, such as Ni, Sn, Pb, Cu, and Fe. The effects of Joule heating, skin, and pinch force are proved to be of lesser importance. The theory gives a good explanation for the experimental results reported by Conrad and co-workers.
关键词:
electric current pulse;grain size;nanocrystalline;conductors
