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INFLUENCE OF SOME FACTORS ON FLUID FLOW IN CONTINUOUS CASTING TUNDISHES

HE Youduo Baotou Institute of Iron and Steel Technology , Baotou , ChinaY.SAHAI The Ohio State University , USA HE Youduo , Professor , Department of Metallurgy , Baotou Institute of Iron and Steel Technology , Baotou , China

金属学报(英文版)

The influence of some factors on velocity field in continuous casting tundishes has been veri- fied by means of computer simulation.These factors are tundish wall inclination;the dimensionless geometric size of tundish,the double inclined wall tundish;the dimension and location of weir and dam.

关键词: continuous casting tundish , null

Static equation of state of bcc iron

Physical Review B

Body-centered-cubic (bcc) iron is one of the most investigated solid-state systems. Using four different density-functional methods, we show that there is a magnetic transition close to the ground-state volume of bcc Fe, which originates from the particular magnetic band structure. The common equation of state functions, used to determine the basic ground-state physical quantities from the calculated total energies, cannot capture the physics of this magnetic transition leading to serious underestimation of the Fe bulk modulus. Ignorance of the magnetic transition found here is reflected by large scatter of the published theoretical bulk moduli of ferromagnetic bcc Fe. Due to the low performance of the exchange-correlation functionals, most of the erroneous results are accidentally in good agreement with the experimental values. The present finding is of fundamental importance, especially taking into account that bcc Fe is frequently used as a test system in assessing the performance of exchange-correlation approximations or total-energy methods.

关键词: generalized-gradient-approximation;total-energy calculations;density-functional approximations;initio molecular-dynamics;magnetic;phase-stability;augmented-wave method;ab-initio;elastic-constants;electron-gas;ultrasoft pseudopotentials

Noncollinear magnetic ground state of PrFeAsO

Europhysics Letters

Noncollinear magnetic investigations of the ground state in PrFeAsO have been performed by the density-functional theory. We calculated the total energy and made structure optimization, and the electronic density of states of PrFeAsO was analyzed. There are three different magnetic structures in PrFeAsO defined by experiments. Based on these magnetic structures, we studied four collinear and four noncollinear cases. The ground state is found to take the ordering proposed by Zhao, in which the FeAs plane is of stripe antiferromagnetism and Pr spins are perpendicular to Fe spins. The electronic density of states indicates that for PrFeAsO the increase of the electron Coulomb interaction leads to a decrease in conductivity. Copyright (C) EPLA, 2011

关键词: high-temperature superconductivity;phase-diagram;oxypnictides;instability

DEFORMATION OF CuZnAl SHAPE MEMORY ALLOYS IN MARTENSITIC STATE

ZHANG Yi Shanghai Institute of Iron and Steel Research , Shanghai , ChinaE.HORNBOGEN Institute for Materials , Ruhr-University Bochum , F.R.G.[Originally published in ACTA METALL SIN(CHINESE EDN)25(3)1989 pp A179—A184.

金属学报(英文版)

Plastic deformation of three CuZnAl shape memory alloys in martensitic state was investi- gated by means of optical and electron metallography,dilatometry and electric resistiviy de- termination.Two of the alloys are in martensitic state at ambient temperature,and the A_f temperature of the third one is far below the ambient temperature.The effect of deformation of alloys in martensitic state on the course and temperature of transformation as well as the hysteresis of transformation cycles has been analyzed and the “effect of the first cycle” has also been discussed.

关键词: shape memory alloy , null , null

SUPERPLASTICITY AND SOLID STATE BONDING OF TITANIUM ALLOYS

R. Ya. Lutfullin , O.A. Kaibyshev , R.V. Safiullin , O.R. Valiakhmetov and M.H. Mukhametrahimov Institute for Metals Superplasticity Problems , Russian Academy of Sciences , Ufa 450001 , Russia

金属学报(英文版)

Experimental results related to solid state weldability of superplastic titanium alloys are presented. A correlation between superplastic flow and enhanced solid state weldability was established. It has been experimentally shown that a drop in the lower superplastic flow temperature with decreasing mean grain size provides an opportunity to decrease the temperature at whicmethods for titanium alloys.

关键词: superplasticity , null , null

STATE TRANSITION IN A FAMILY OF GENERALIZED FIBONACCI LATTICES

Zeitschrift Fur Physik B-Condensed Matter

We study the electronic properties of a family of generalized Fibonacci lattices associated with the sequences which are given by the inflation rule (A, B) --> (AB(n), A) with n > 1. Analytical and numerical analyses reveal the existence of a state transition phenomenon, i.e. a transition from the local density of states with a smooth behavior in some energy regions to another one without any smooth part.

关键词: one-dimensional quasicrystals;renormalization-group;quasi-crystals;extended states;green-functions;localization;spectrum;model;chain;maps

Solid-state and liquid-state interfacial reactions between Sn-based solders and single crystal Ag substrate

Journal of Alloys and Compounds

Growth kinetics and interfacial morphologies of the intermetallic compounds (IMCs) between single crystal Ag and Sn-4Ag, Sn-3Cu and Sn-37Pb solders were investigated by solid-state aging at 160 degrees C and liquid-state aging at 260 degrees C. Isothermal equation of chemical reaction and phase diagrams were used to explain the effects of Ag, Cu and Pb on the growth kinetics of IMCs under solid-state and liquid-state aging conditions. The diffusion coefficients for the three solder joints of Sn-4Ag/Ag, Sn-3Cu/Ag and Sn-37Pb/Ag were calculated after solid-state and liquid-state aging. It is found that Pb can effectively retard the growth of IMCs during liquid-state aging but has little influence on the growth rate of IMCs during the solid-state aging. Some local small cracks were frequently observed in the Cu(6)Sn(5) particles near interfaces of the Sn-3Cu/Ag solder joints after solid-state aging for several days. However, there were no such local small cracks when solders or interfaces did not contain the Cu(6)Sn(5) particles after the same aging time. (C) 2008 Elsevier B.V. All rights reserved.

关键词: Ag single crystal substrate;Lead-free solder;Intermetallic compounds;(IMCs);Growth kinetics;Local cracks;lead-free solders;electroless ni(p) metallization;intermetallic;compound;cu-sn;joints;ni;bi;nanoindentation;microstructure;wt.percent

Studies of the ferromagnetic state in quasi-one-dimensional organic polymer ferromagnets

Communications in Theoretical Physics

The possible ferromagnetic ground state of pi-conjugated alternant hydrocarbon chains with unequal number of atoms on two sublattices is studied by the peierls-Hubbard model. Allowing for full lattice relaxation, a set of self-consistent iterative equations are established to study this system. The stabilities of the possible ferromagnetic ground states with respect to two kinds of unsymmetric site energies are also studied. We find that the ground state of the system is a stable ferromagnetic state as a result of the topological structure of the network and the electron-electron interaction. And the unsymmetric site energies, induced by substitutions, will severely weaken the stability of the ferromagnetic ground state.

关键词:

Theoretical model of an organic ferrimagnetic state for a bipartite lozenge chain

Physical Review B

A model for one-dimensional bipartite lozenge chain is proposed. By unrestricted Hartree-Fock approximation, we find that the system should exhibit ferrimagnetic ordering for a half filled band. In the ground state, the energy levels of electrons will split off with respect to different spins and the electrons along the chain will form an antiferromagnetic spin-density wave. The ground state of the system will be more stable with increasing of the on-site Hubbard term.

关键词: ferromagnet

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