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Unusual Behaviour of Dislocation Velocity Exponent in Dislocation Multiplication Model

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Journal of materials Science & Technology 1998年第3期14卷 215-218页

作者： Xaowei WANG(international Centre for materials physics, Institute of Metal Research, chinese academy of Sciences,shenyang 110015, china. international Centre for materials physics Institute of Metal Research Chinese Academy of Sciences Shenyang 110015 China

The chaotic behaviour of dislocation multiplication process was investigated. The change of Lyapunov exponent which is used to determine the stability of quasi-periodic and chaotic behavior as well as that of equilibrium points, and periodic solution was reported by using an iteration model of dislocation multiplication. An unusual behavior of Lyapunov exponent and Feigenbaum exponent which respond to the geometric convergence of orbit from bifurcation to chaos was shown by dislocation velocity exponent m and there is a distinction on the tendency of convergence for the dislocation multiplication model when it was compared with logistic map. It is reasonable for the difference to be analyzed from the materials viewpoint. (Edited author abstract) 9 Refs.

关键词： Unusual Behaviour of Dislocation Velocity Exponent in Dislocation Multiplication Model

Multirange Fractals in materials: Applications to Fracture and Mechanical Alloying under Ball Milling

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Journal of materials Science & Technology 1997年第4期13卷 255-259页

作者： Chiwei LUNG(international Centre for materials physics, Institute of Metal Research,chinese academy of Sciences, shenyang 110015, china. international Centre for materials physics Institute of Metal Research Chinese Academy of Sciences Shenyang 110015 China

A new model of multirange fractals is proposed to explain the experimental results observed on the fractal dimensions of the fractured surfaces in materials. A new explanation to the Williford's multifractal curve on the relationship of fractal dimension with fracture properties in materials has been given. It shows the importance of fractorizing out the effect of fractal structure from other physical causes and separating the appropriate range of scale from multirange fractals. Mechanical alloying process under ball milling as a non-equilibrium dynamical system has been also analyzed.

关键词： Ball Applications to Fracture and Mechanical Alloying under Ball Milling Multirange Fractals in materials

Role of Edge and Screw Dislocations in Deformation of Metals

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Journal of materials Science & Technology 1995年第2期11卷 133-136页

作者： Chiwei LUNG(international Centre for materials physics, Institute of Metal Research,chinese academy of Sciences, shenyang, 110015, china. Inst of Metal Research Shenyang China

It was widely accepted that the screw dislocation is responsible for the strong temperature dependence of the yield stresses observed in bcc metals. In this paper, we show the role of edge dislocations in the deformation of metals and point out that in some cases, its main contribution to the plastic flow behaviour cannot be ignored.

关键词： Crystal structure

Dislocation Velocity Exponent and the Strain Rate

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Journal of materials Science & Technology 2001年第3期17卷 363-366页

作者： Hongyan LIU and Xiaowei WANG international center for Material physics, Institute of Metal Research, chinese academy of Sciences, shenyang 110016, china.E-mail: liu@*** chinese Acad Sci Met Res Inst Int Ctr Mat Phys Shenyang 110016 Peoples R China

The process of dislocation multiplication has been described hv chaos theory, trying to reveal the connection between the microstructures on the mesoscopic scale and the mechanical properties of material on the macroscopic scale. The relationship between the dislocation velocity exponent and the maximum of strain rate is given. The results obtained from logistic equation with exponent and the dislocation multiplication dynamic equation are compared. A scale law in one-dimension-map model with exponent is shown when the exponents of equations are changed.

关键词： Dislocation Velocity Exponent and the Strain Rate

Universality and Specificity of Fractal Dimension of Fractured Surfaces in materials

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Journal of materials Science & Technology 2000年第1期16卷 1-4页

作者： Chiwei LUNG and Shenggang WANG (international Centre for materials physics, Institute of Metal Research, chinese academy of Sciences, shenyang 110015, china. international Centre for materials physics Institute of Metal Research Chinese Academy of Sciences Shenyang 110015 China

After calculation on the fracture angles under various conditions of specific surface energies with different symmetry operations of rotation, the complicated behavior of dependence of fractal dimension on the structure of crystal is shown. It is found that the crack propagates along the weakest crystal plane no matter what the direction of the maximum stress is if the anisotropy is sufficiently strong; and then, the fractal dimension of the fractured surfaces might be determined by the approximate fractal structure already existed in the material. Specificity of the fractal dimension of fractured surfaces would be easy to appear in this case. Reversely, the crack propagates along the direction of the maximum stress no matter what direction of the weakest crystal plane is if the anisotropy is sufficiently weak. Universality of the fractal dimension of fractured surfaces would be possible to appear in this case. In many real materials, universality and specificity of the materials are associated. The fractal dimension measured may more or less be influenced by the structure of materials and it shows its universality through the specificity of materials.

关键词： Universality and Specificity of Fractal Dimension of Fractured Surfaces in materials

Effects of Distribution of Induced Defects on Positron Diffusion

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Journal of materials Science & Technology 2000年第1期16卷 73-75页

作者： Xinzhang ZHOU, Jian JIANG and Chiwei LUNG (international center for materials physics, Institute of Metal Research, chinese academy of Sciences, shenyang 110015, china. international center for materials physics Institute of Metal Research Chinese Academy of Sciences Shenyang 110015 China

The effects of distribution of induced defects on the positron diffusion was studied by using the point-source diffusion model and 6 function method.

关键词： Effects of Distribution of Induced Defects on Positron Diffusion

Ni-based Ni-Fe-B-Si-Ta bulk metallic glasses

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Science china.physics,Mechanics & Astronomy) 2010年第3期53卷 440-444页

作者： ZHU ChunLei1, WANG Qing1, ZHAO YaJun1, WANG YingMin1, QIANG JianBing1 & DONG Chuang1,21 Key Lab of materials Modification (Ministry of Education), School of materials Science and Engineering, Dalian University of Technology, Dalian 116024, china.2 international center for materials physics, chinese academy of Sciences, shenyang 110016, china 1. Key Lab of materials Modification (Ministry of Education) School of Materials Science and Engineering Dalian University of Technology Dalian 116024 China2. International Center for Materials Physics Chinese Academy of Sciences Shenyang 110016 China

The glass-forming ability and properties of Ni-based Ni-Fe-B-Si-Ta bulk metallic glasses are explored in this work. The alloy compositions are determined by using a combination of the cluster line approach, the multi-alloying strategy and the substitutions of similar elements. Bulk metallic glasses with diameters of 3 mm take shape at compositions formulated under the clus- ter-plus-glue-atom model [M9B]B~[(Ni1-xFex)7.71(Si0.66Ta0.34)1.29B]B0.94=(Ni1-xFex)70.5B17.7Si7.8Ta4, x=0.35–0.45, where the bracketed part is the cluster and the unbracketed part is the glue atoms. These alloys exhibit good magnetic properties. The maximum Is is found in the (Ni0.55Fe0.45)70.5B17.7Si7.8Ta4 alloy which reaches 0.51 T, with its Hc as low as 8.5 A/m. Interestingly, these alloys display dual glass transitions at (Ni0.65Fe0.35)70.5B17.7Si7.8Ta4, (Ni0.60Fe0.4)70.5B17.7Si7.8Ta4 and (Ni0.55Fe0.45)70.5B17.7- Si7.8Ta4 as unveiled by Temperature-Modulated Differential Scanning Calorimetry.

关键词： bulk metallic glasses cluster Ni-Fe-based alloys Modulated Differential Scanning Calorimetry

Energy Spectrum of YAG:Cr3+ and Thermal Shifts of Its R Lines

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Communications in Theoretical physics 2005年第7期44卷 165-170页

作者： MA Dong--Ping CHEN Ju--Rong Department of Applied physics, Sichuan University, Chengdu 610065, china.international Centre for materials physics, the chinese academy of Sciences, shenyang 110015, china Department of Applied physics Sichuan University international Centre for materials physics the Chinese Academy of Sciences

Traditional ligand-field theory has to be improved bv taking into account both "pure electronic" contributionand electron-phonon interaction one （including lattice-vitbrational relaxation energv）. By means of improved ligand-fieldtheory, R1, R2, R3′, R2′, and R1′ lines, U band, ground-state zero-field-splitting （GSZFS） and ground-state g factors aswell as thermal shifts of R1line and R2line of YAG:Cr3+have been calculated. The results are in very good agreementwith the experimental data. In contrast with ruby, the octahedron of ligand oxygen ions surrounding the central Cr3+ion in YAG:Cr3+is compressed along the [111] direction. Thus, for YAG:Cr3+and ruby, the splitting of t23 4A2(or t23 2E)has opposite order, and the trigonal-field parameters of the two crystals have opposite signs. In thermal shifts of R1andR2lines of YAG:Cr3+, the tetnperature-dependent contributions due to EPI are dominant.

关键词： improved ligand-field theory electron-phonon interaction Stokes shift energy spectrum thermal shift g factor

Positron Lifetime Study of the Single-Phase B2 Ni_(100-x)Al_x and Ni_(50-x)Co_xAl_(50) Intermetallics

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Journal of materials Science & Technology 2000年第4期16卷 379-382页

作者： Rongshi CHEN, Jianting GUO and Wenlong ZHOU (Department of Superalloys, Institute of Metal Research, chinese academy of Sciences, shenyang 110015, china. Liangyue XIONG (international center for materials physics, and Liaoning Key Laboratory for materials Department of Superalloys Institute of Metal Research Chinese Academy of Sciences Shenyang 110015 China Liaoning Key Laboratory for materials and Hydrogen Institute of Metal Research Chinese Academy of Sciences Shenyang 110015 China

In order to understand the point defect structure in NiAl Intermetallic compound, the positron lifetime in binary Ni_(100-x)Al_x (53≥x≥45) and ternary B2 Ni_(50-x)Co_xAl_(50) (x=0, 5, 10, 15) intermetallic compounds as a function of composition were measured. It is shown that the positron lifetime spectra of these compounds can be consistently expressed by single-component lifetimes. The positron lifetime value in ternary Ni_(50-x)Co_xAl_(50) alloy is independent of Co content and equal to that detected in both stoichiometric and Al-rich NiAl. From an analysis of the present results, it is suggested that the constant lifetime ofт≈180 ps should be ascribed to saturation trapping and annihilation of positron exclusively at Ni vacancy, no evidence for the presence of Al vacancy is available.

关键词： x)Co_xAl Intermetallics x)Al_x and Ni