材料期刊网

Friction Stir Welding of Discontinuously Reinforced Aluminum Matrix Composites: A Review

D.Wang , B.L.Xiao , D.R.Ni , Z.Y.Ma

金属学报(英文版) doi:10.1007/s40195-014-0143-2

关键词:

Two-step magnetization in a spin-chain system on the triangular lattice: Wang-Landau simulation

Physical Review B

The Wang-Landau algorithm is used to study the thermodynamic and magnetic properties of triangular spin-chain system based on two-dimensional Ising model in order to understand the magnetic-order dynamics in Ca(3)Co(2)O(6) compound. The calculated results demonstrate that the equilibrium state of the rigid spins produces the two-step magnetization curve at low temperature even when the random-exchange term is considered. This work indicates that the four-step magnetization behavior observed experimentally must be due to the nonequilibrium magnetization.

关键词: calcium compounds;exchange interactions (electron);Ising model;magnetisation;thermodynamics;one-dimensional ca3co2o6;density-of-states;compound ca3co2o6;phase-diagram;proteins;crystal

The effects of 3d alloying elements on grain boundary cohesion in gamma-iron: a first principles study on interface embrittlement due to the segregation

Journal of Physics-Condensed Matter

By the use of a first principles density functional theory, two kinds of models, namely the Rice-Wang thermodynamics model and the Seah quasi-chemical model, are employed to evaluate the embrittling tendency of a grain boundary (GB) due to the 3d element segregation. The first principles method based on those two models is appropriate for calculating the chemical and structural relaxation contributions to the changes of GB cohesion with the 3d segregants. The effects of the 3d transition elements, such as Ti, V, Cr and Mn, on a stable fcc Fe Sigma 11 [1 (1) over bar0]/(11 (3) over bar) GB are studied and the difference between these two models is interpreted. When the chemical and the structural relaxation effects are taken into account, the calculated results for these two models are coincident for most of the elements studied, except for chromium. After analysing their chemical bonding in detail, we find that this discrepancy may be attributable to a lower susceptibility of the Seah model to the bonding anisotropy caused by Cr in the GB. It is proposed that the Seah model should be prudently used for some elements, especially those lying in the middle of a transition period.

关键词: phosphorus;adsorption;interstitials;decohesion;magnetism;systems;cluster;metals;boron

Energy levels of the d*(8) electron and d*(2) hole system

Physical Review B

In the investigation of the optical and magnetic properties of the semiconductors containing transition-metal ions, the one-electron orbital cannot be treated with a pure d orbital because of a strong covalence. This paper presents the energy matrix of the d*(8) and d*(2) (d* means a modified d function) system, in which the covalence is described by two covalent factors. The differences between the matrix diagonal elements of the t(2)(m)e(n) term of the d*(8) system and the t(2)(6-m)e(4-n) term of the d*(2) system vary with m and n. The d(N) electron system can be explained with the d(10-N) hole system because the difference between the energy matrix of the d(N) and d(10-N) systems has a fixed value. However, this kind of simple relation does not exist for the d*(N) and d*(10-N) systems when the covalence is considered. A numerical calculation shows that the variation of the energy levels with the covalence for Ni2+ in the d*(8) electron system is larger than that in the d*(2) hole system. The calculated energy levels obtained from the d*(8) matrix are in good agreement with the experimental data of the Ni2+ ion for ZnS:Ni and ZnSe:Ni. This suggests that the d*(8) electron system instead of the d*(2) hole system should be used in the investigation of optical and magnetic properties of semiconductor containing Ni2+ ions.

关键词: zns-ni;absorption;vanadium;impurities;spectra;ions

Ion sputter erosion in metallic glass-A response to "Comment on: Homogeneity of Zr(64.13)Cu(15.75)Ni(10.12)Al(10) bulk metallic glass" by L-Y. Chen, Y-W. Zeng, Q-P. Cao, B-J. Park, Y-M. Chen, K. Hono, U. Vainio, Z-L. Zhang, U. Kaiser, X-D. Wang, and J-Z Jiang J. Mater. Res. 24, 3116 (2009)

Journal of Materials Research

The morphology of the dark and bright regions observed by transmission electron microscopy for the Zr(64.13)Cu(15.75)Ni(10.12)Al(10) bulk metallic glass strongly depends on the ion beam parameters used for ion milling. This indicates that the ion beam could introduce surface fluctuation to metallic glasses during ion milling.

关键词: room-temperature

液晶材料与3D显示

张兴 , 郑成武 , 李宁 , 周兴丹 , 李正强 , 华瑞茂

液晶与显示 doi:10.3788/YJYXS20122704.0448

介绍了3D显示的基本原理,重点介绍了目前3D显示的主流技术类型,包含了眼镜式3D技术以及裸眼式3D技术,其中眼镜式3D技术包含色差式3D技术、偏光式3D技术和主动快门式3D技术;裸眼式3D技术包含视差屏障式3D技术、柱状透镜式3D技术、指向光源式3D技术和多层显示式3D技术.阐述了各种3D显示技术的基本实现原理和应用领域、并对涉及液晶显示的几种3D技术的优缺点进行了对比.结合液晶材料的特点与3D液晶显示的实际要求,阐述了3D液晶面板对液晶材料快速响应方面的要求,以及液晶透镜对液晶材料光学各向异性参数的要求.

关键词: 3D显示 , 眼镜式3D显示 , 裸眼式3D显示 , 液晶材料

COMPARISON OF FATIGUE AND CREEP BEHAVIOR BETWEEN 2D AND 3D-C／SiC COMPOSITES

D.Han , S.R.Qiao , M.Li , J.T.Hou , X.J.Wu

金属学报(英文版)

The differences of tension-tension fatigue and tensile creep characters of 2D-C/SiC and 3D-C/SiC composites have been scrutinized to meet the engineering needs. Experiments of tension-tension fatigue and tensile creep are carried out under vacuum high temperature condition. All of the high temperature fatigue curves are flat; the fatigue curves of the 2D-C/SiC are flatter and even parallel to the horizontal axis. While the tension-tension fatigue limit of the 3D-C/SiC is higher than that of the 2D-C/SiC, the fiber pullout length of the fatigue fracture surface of the 3D-C/SiC is longer than that of the 2D-C/SiC, and fracture morphology of the 3D-C/SiC is rougher, and pullout length of the fiber tows is longer. At the same time the 3D-C/SiC has higher tensile creep resistance. The tensile curve and the tensile creep curve of both materials consist of a series of flat step. These phenomena can be explained by the non-continuity of the damage.

关键词: 2D-C/SiC , null , null

Surface properties of 3d transition metals

Philosophical Magazine

Using the projector augmented wave method within density functional theory, we present a systematic study of the layer relaxation, surface energy and surface stress of 3d transition metals. Comparing the calculated trends for the surface energy and stress with those obtained for 4d and 5d metals we find that magnetism has a significant effect on the surface properties. Enhanced surface magnetic moments decrease the size of the surface relaxation, lower the surface energy and surface stress, leading to compressive stress in Cr and Mn.

关键词: surface relaxation;surface energy;surface stress;magnetic transition;metals;density functional theory;full charge-density;initio molecular-dynamics;total-energy;calculations;augmented-wave method;ab-initio;electronic-structure;atomic volume;work function;basis-set;relaxation

R&D STATUS ON INTERMETALLICS IN CHINA

CHEN Guoliang(State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing Beijing 100083 , China)SHI Changxu (Academia Sinica , Beijing 100864 , China)

金属学报(英文版)

This paper briefiy introduces the R&D of intermetallics in China. R&D on intermetallics in a national scale in China began near ten years ago. The investigation in past years focused on the fundamental research and materials development. A significant progress has been made. Various components that made of Ti3Al Ni3Al, TiAl and Fe3Al have been successfully manufactured Some of them have been evaluted. It is expected that some intermetallic alloys will be produced in an industrial scale in the near future.

关键词: :intermetallic alloys , null , null , null

R & D ACTIVITIES ON AEROSPACE MATERIALS IN KOREA

H.M. Kim(Korea Institute of Machinery and Materials , Korea Manuscript received 26 August 1996)

金属学报(英文版)

This paper briefly reviews research and development programs in Korean aerospace industry,with an emphasis on aircraft materials technology. International collaborations in these areas are outlined and the R & D activities are highlighted against the　background of the national economy.It is shown that the investment from government agencies and large enterprises has led to healthy development of aerospace materials industries in Korea.

关键词: :R & D , null , null , null