GUO Wenquan WANG Jingtang Laboratory of Rapidly Solidified Non-Equilibrium Alloys
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Institute of Metal Research
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Academia Sinica
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Shenyang
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China
金属学报(英文版)
Considering the availability and derivation of Roscoe's equation for absolute viscosity calcula- tion,the method to adopt λ_0 value,so-called λ_f,was proposed by experimentally deter- mining relational curve of the measured height,H,of metal melt vs logarithmic oscillation decrement,λ,extrapolating H into zero,if such corresponding λ value is taken.Experimental results show that the proposed method not only satisfies the availability of original equation but also eliminate the effects of:“end and slippage”,so as to improve the accuracy for liquid Cu and Sn examinations.
关键词:
liquid metal
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null
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null
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ZHANG Lixin NING Hua Laboratory of Corrosion Science
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Institute of Corrosion and Protection of Metals
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Academia Sinica.Shenyang
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ChinaZHOU Jing LI Liguang Institute of Metal Research
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Academia Sinica
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Shenyang
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China Professor
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Institute of Corrosion and Protection of Metals
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Academia Sinica
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Shenyang 110015
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China
金属学报(英文版)
The relations between the non-equilibrium segregation process of P and the change of the texture in Fe-P alloys have been studied by analytical electron microscope and orientation distribution function.It was shown that P segregated preferentialy on the{110}slip planes, the P segregation structures with repeating cycle a=1.582 nm form at 450℃.<001>// ND direction abated.<111>//ND direction heightened.And{111}<110>has a tendancy to transform into{111}<143>texture in recovering process.{111}<143>direction trans- forms into{111}<112>direction after recrystalizing.A model to describe the effects of non-equilibrium segregation structures of P on orientation change was proposed and em- ployed to interpret the experiment results.
关键词:
Fe-P Alloy
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null
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null
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CHU Youyi ZHANG Sanhong HE Xinlai KE Jun(T.Ko) University of Science and Technology Beijing
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China CHU Youyi Professor
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The Nonferrous Metals Society of China
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Room 602
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B12
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Fuxing Road
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Beijing 100814
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China
金属学报(英文版)
In consideration of the local equilibrium among vacancies,solute atoms and vacancy-solute atom complexes and the influence of equilibrium grain boundary segregation,theoretical dy- namic formulas for non-equilibrium grain boundary segregation of solute have been derived on the basis of the vacancy-dragging mechanism.Theoretical calculation by computer has been carried out for the non-equilibrium segregation of boron to austenitic grain boundaries during isothermal holding and continuous cooling after heating at high temperatures.The re- suits agree well with those obtained from experiments.
关键词:
solute
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null
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null
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Ruiheng WU
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Xueyu RUAN
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Hongbing ZHANG
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T.Y.Hsu
材料科学技术（英文）
By combining the α/γ interface migration and the carbon diffusion at the interface in Fe-C alloys, a mathematical model is constructed to describe the mixed-control mechanism for proeutectoid ferrite formation from austenite. In this model, theα/γ interface is treated as non-equilibrium interface, i.e., the carbon concentration of austenite at γ/α interface is obtained through theoretical calculation, instead of that assumed as the local equilibrium concentration. For isothermal precipitation of ferrite in Fe-C alloys, the calculated results show that the rate of interface migration decreases monotonically during the whole process, while the rate of carbon diffusion from γ/αinterface into austenite increases to a peak value and then decreases. The process of ferrite growth may be considered as composed of three stages: the period of rapid growth, slow growth and finishing stage. The results also show that the carbon concentration of austenite at γ/αinterface could not reach the thermodynamic equilibrium value even at the last stage of ferrite growth.
关键词:
Proeutectoid ferrite precipitation
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null
Materials Science and Engineering a-Structural Materials Properties Microstructure and Processing
A lot of non-equilibrium high technologies have recently been developed in materials processing, such as spray forming; metal atomization by electric fluid dynamics; self-propagating high temperature synthesis; in situ contact reaction process in melt for making composites and electropulsing effect on structure modification and damage reversal etc. A series of non-equilibrium thermophysical problems arise consequently with these high technologies. Not only the real-time measurements are difficult to deal with, but also the principle analyses need to be treated carefully. It would be found that some of the normal thermophysical rules should be evaluated again, when the thermophysical processes under extreme conditions are further studied. Some possible ways for solving these abnormal thermophysical problems are tentatively suggested in this paper, such as the reconstruction of governing functions; the simplified treatment of complex processes and making use of the rules of other disciplines etc. It is known from these examples that a series of non-equilibrium thermophysical problems arising from recent high technologies of materials processing are remained to be actively studied. It gives a virgin land for thermophysicists to explore. (C) 2000 Elsevier Science S.A. All rights reserved.
关键词:
biomimetic;materials processing;non-equilibrium;thermophysical;problems
CAl Yingwen
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MAO Xiemin
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LI Jianguo
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FU HengzhiNorthwestern Polytechnieal University
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Xi'an
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China Manuscript received 14 March
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1994
金属学报(英文版)
Theoretical model for non -equilibrium solidification is constructed with consideration of diffuse interface and multiphase fluctuation. It can he degenerated to Aziz continuous growth model in the case of mono-atomic approximation. for large undercooling, the change of heat capacity should not he neglected and it usually gives an increase in the interface partition coefficient. Solute trapping may happen at a rather slow growth rate compared with that predicted by other models, because the undercooling and structural relaxation ahead of the S/ L interface lowers the interfacial diffusivity to a great extent. Plase fluctuation has two contending effects, decrease in energy barrier and increase in atomic dragging, therefore exerts dual influences on the partition coefficient.
关键词:
diffuse interface
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null
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Physica Status Solidi B-Basic Research
The morphologies of the deposits SnI2 and CdI2, which formed on the surface of a silicon crystal during vapor-solid transition, were studied. The SnI2 fractal structures and the CdI2 self-organizing structures were observed by scanning electron microscopy. It is most significant that the SnI2 fractal structures were composed of nanograins grown at the advancing front of SnI2 crystal accumulation, and showed a transient from equilibrium to non-equilibrium growth. The transient occurred as the cooling rate was increased up to 1000 K/min. The CdI2 self-organizing sunflower-like structures were composed of CdI2 nanocrystals, and indicated an anomalous growth mechanism. The experimental results suggest that the iodide thin films can give rise to fractal structures or self-organizing structures resulting from non-equilibrium growth processes.
关键词:
fractal clusters
Xiaolong CUI
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Lai WANG
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Min QI
材料科学技术（英文）
Using X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimeter (DSC) and optical microscopy, phase transformation of Cu-Cr alloys with various compositions during mechanical alloying process has been investigated. Besides the formation of supersaturated solid solution, the results show that a kind of amorphous oxide formed in the process, and the addition of carbon has obviously effect on the suppression of oxidation and the deoxidization of oxide. The reactive milling has a remarkable effect on the behavior of oxidation.
关键词:
P. Wu
金属学报(英文版)
The development of non-equilibrium segregation of boron at grain boundaries in Fe-40%Ni alloy during continuous cooling process was experimentally observed with boronParticle Tracking Autoradiography (PTA) and Transmission Electron Microscopy(TEM). The samples with 10ppm boron were cooled at 2℃/s to 1040, 980, 920,860, 780 and 640℃ respectively after pre-heat treatment of 1150℃ for 15min witha Gleeble-1500 heat simulating machine, then water quenched to room temperature.The width of segregation layer and boron depletion zone, rich factor and other pc-rameters were measured by a special image analysis system. The experimental resultsof PTA show that the grain boundary segregation of boron during cooling process is adynamic process and the development of the non-equilibrium segregation experiencesthree stages: first increases rapidly from 1150 to 1040℃, then gently from 1040 to860℃, and rapidly again from 860℃ to 640℃. The width of boron depletion zoneincreases from about 11μm at 1040℃ to 26μm at 640℃. TEM observation showsthat boron precipitates exist at grain boundaries when the samples are cooled to below860℃. The experimental phenomena are briefly discussed.
关键词:
boron
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null
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CHEN Niug
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YU Zongsen University of Science and Technology Beijing
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Beijing
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China professor
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Department of Materials Physics
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University of Science and Technology Beijing
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Beijing 100083
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China
金属学报(英文版)
Si segregation was observed in the vacancy condensation pits,formed by supersaturated vacancies beneath the oxidation layer of Al-0.35wt-%Si alloy,by optical microscopy,X- ray photoelectron spectroscopy and microhardness tests.This phenomenon could only be explained by vacancy-Si complex inducing non-equilibrium segregation.
关键词:
non-equilibrium segregation
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null
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null
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