材料期刊网

IF钢退火过程中再结晶数学模型的探讨

叶卫平 , 陈铁群 , R.Le Gall , G.Saindrenan

金属学报 doi:10.3321/j.issn:0412-1961.2001.02.008

采用传统JMAK模型和一种新的再结晶模型研究了经70%,80%和90%冷变形的IF(无间隙原子)钢再结晶过程.实验结果表明,以In(-In(1-xv))为纵坐标和In t为横坐标进行回归,JMAK图呈直线关系,其JMAK指数n在1.33-2.51之间,低于理想的JMAK指数.采用一个新的再结晶模型对IF钢的再结晶过程进行了分析,用非线性回归方法回归出该模型的参数.该模型可将再结晶过程与其组织参数联系起来,具有明确的物理意义,能较好地用于描述IF钢再结晶过程.

关键词: IF钢 , 再结晶过程 , 数学模型

Fractal structures precipitated from A gall of patient

Physica B-Condensed Matter

Three kinds of structures precipitated from the A gall of a patient were observed on the same samples by a field emission gun-scanning electron microscope (FEG-SEM). They were branching fractal structures, dendritic structures, and irregular crystalline grains. The fractal structures consisted of numerous granules that mostly disconnected each other. The dendrites were connected basically together. The tiny crystalline grains were of complicated shapes. A precipitation-aggregation-branching (PAB) model was used to explain growth mechanism of the fractal structure. Energy dispersive X-ray spectroscopy (EDS) was employed to measure chemical composition of three kinds of precipitates, as well as the A gall matrix. The experimental results reveal that saline or salt played an important role to the formation of the fractal structure, and also to that of the dendritic structure and crystalline grain. There may be relationship between the fractal in the A gall sample and fractal in gallstones. (c) 2005 Elsevier B.V. All rights reserved.

关键词: fractal structure;dendrite;A gall;precipitation;tear;growth

Effect of Doping and High-Temperature Annealing on the Structural and Electrical Properties of Zn_1-XNi_XO(0≤X≤0.15) Powders

Hakan Colak

材料科学技术（英）

This paper reported the synthesis, crystal structure and electrical conductivity properties of Ni-doped ZnO powders (i.e. Zn_1-XNi_XObinary system, X=0, 0.0025, 0.005, 0.0075 and in the range 0.01≤X≤0.15). I-phase samples, which were indexed as single phase with a hexagonal (wurtzite) structure in the Zn_1-XNi_XObinary system, were determined by X-ray diffraction (XRD). The widest range of the I-phase was determined as 0≤X≤0.03 at 1200°C; above this range the mixed phase was observed. The impurity phase was determined as NiO when compared with standard XRD data, using the PDF program. We focused on single I-phase ZnO samples which were synthesized at 1200°C because of the widest range of solubility limit at this temperature. It was observed that the lattice parameters a and c of the I-phase decreased with Ni doping concentration. The morphology of the I-phase samples was analyzed with a scanning electron microscope. The electrical conductivity of the pure ZnO and single I-phase samples were studied by using the four-probe dc method at temperatures between 100 and 950°C in air atmosphere. The electrical conductivity values of pure ZnO and 3 mol% Ni-doped ZnO samples at 100°C were 2×10^-6 and 4.8×10^-6Ω^-1?cm^-1, and at 950°C they were 1.8 and 3.6Ω^-1?cm^-1, respectively. In other words, electrical conductivity increased with Ni doping concentration.

关键词: II-VI semiconductors

Acoustic emission inspection of Portevin-Le Chatelier effect and deformation mechanisms of two Mg-Li-Al alloys

Journal of Materials Science

In this paper, Portevin-Le Chatelier (PLC) effect of LA41 magnesium alloy is reported. With increasing strain rate, both ultimate tensile stresses (sigma(b)) and 0.2% proof (sigma(0.2)) stresses increase, while serrations become less severe. Major acoustic emission (AE) peaks appear at the end of elastic region, and transform to burst type signals in the plastic range. In another alloy containing less Li (LA11), serrations are absent and major AE peak values are considerably lowered. Additionally, PLC effect disappears in LA41 after annealing. The role of twins is discussed in details. Actual causes for AE activity during deformation are also proposed.

关键词: tensile deformation;magnesium alloys;bands;az31

A Macroscopic Model for the Portevin-Le Chatelier Effect

材料科学技术（英）

关键词:

R-line thermal shift and thermal broadenings of R, R' and B lines for ruby

Communications in Theoretical Physics

The unified theoretical calculation of thermal shifts (TS) of R-1 and R-2 lines and thermal broadenings (TB) of R, R' and B lines for ruby was carried out for the first time. The calculated results are in very good agreement with a great number of experimental data. Especially by using quantum theory and taking into account all the admixtures of wavefunctions within d(3) electronic configuration, all the Gamma M in electron-phonon interaction (EPI), the electronic energy spectrum and lattice-vibration Spectrum, the very important contributions to TS and TB from single-phonon direct process were theoretically calculated in detail. The microscopic essentials of various contributions are revealed, and the mistakes in previous work are remedied.

关键词: diamond anvil cell;pressure measurement;spectroscopy;temperatures

Theoretical calculations of thermal broadenings and transition probabilities of R, R ' and B line-groups for ruby

Communications in Theoretical Physics

On the basis of the unified calculation of the thermal shifts of R-1 line, R-2 line and ground-state-splitting as well as the thermal broadenings of R, R' and B line-groups for ruby, by taking into account all the levels and admixtures of wavefunctions within d(3) electronic configuration and all the GammaM in electron-phonon interaction, the transition probabilities of direct and Raman processes have theoretically been calculated. The thermal broadenings, of R, R' and B line-groups have successfully been interpreted in terms of the direct and Raman processes of acoustic phonons. The theoretically predicted transition probabilities are in good agreement with the experimental ones.

关键词: crystal fields;electron-phonon interaction;thermal broadening;transition probability;direct and Raman processes;shifts

Phase diagram of R-Fe-Co pseudoternary system with R <= 33.3% (mole fraction, R = Sm0.5Dy0.5)

Transactions of Nonferrous Metals Society of China

Phase equilibria of the R-Fe-Co pseudoternary system with R less than or equal to 33.3% ( mole fraction, R = Sm0.5Dy0.5) were determined in an isothermal section at 1073 K and a vertical section of RFe2-RCo2 by using OM, X-ray diffractometer, EP-MA DTA techniques. There are seven intermetallic phases: (Sm, Dy) (Fe, Co)(2), (Sm, Dy) (Fe, Co)(3), (Sm, Dy)(6) (Fe, Co)(23), (Sm, Dy)(2) (Fe, Co)(7), (Sm, Dy) (Fe, Co)(5), Th2Ni17-type and Th2Zn17-type (Sm, Dy)(2)(Fe, Co)(17). The (Sm, Dy)(6)(Fe, Co)(23) phase dissolves 36% Co(mole fraction) at 1073 K. However, the (Sm, Dy)(2)(Fe, Co)(7) phase in R-2(Fe1-xCox)(7) alloys dissolves about 19% Fe(mole fraction) at 1073 K.

关键词: rare earth-iron-cobalt;phase diagram;structure;compounds;sm-co;magnetic-properties;binary-system;magnetostriction

NEUTRON DIFFRACTION STUDY ON R_2Fel_(17)N_x(R=Y,Dy,Nd)

YANG Jilian ZHANC Baisheng DINC Yongfan China Institute of Atomic Engergy , Beijing , ChinaYANG Yingchang ZHANG Xiaodong Peking University , Beijing , ChinaPAN Shuming General Research Institute for Non-Ferrous Metals , Beijing , China associate professor , P.O.Box 275 , Branch No.30 , Beijing 102413 , China

金属学报(英文版)

The N occupying sites and magnetic structures in R_2Fe_(17)N_x(R=Y,Dy,Nd)are de- termined by neutron diffraction.The effects of the site occupation of N on magnetic properties are discussed primarily.

关键词: neutron diffraction , null , null , null , null , null

SPIN REORIENTATION AND EXCHANGE INTERACTIONS IN (ND, R)2FE14B (R = Y, GD)

Journal of Magnetism and Magnetic Materials

Exchange fields in both (Nd, Y)2Fe14B and (Nd, Gd)2Fe14B series are determined by analyzing spin reorientation. Results calculated for the two systems suggest that the R-R exchange interactions between R ions are comparable with the crystal-field interaction and that their effect might be taken into account for reproducing the spin-reorientation temperature.

关键词: magnetization process;crystal;nd2fe14b;r2fe14b;transition