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Influencing Factors For Obtaining Ultrafine Austenite Grains With Initial Microstructure Of Warm-Rolled Ferrite/Pearlite

S.J. Yao , L.X. Du , X.H. Liu , G.D. Wang

金属学报(英文版)

Three warm-rolled ferrite/pearlite microstructures were prepared by rolling at 500℃, and the austenitizing characteristics were discussed in conjunction with deformation during the heating stage. The results indicated that the final austenite grain size was sensitive to the deformation direction of the initial warm-rolled microstructure. The transient microstructure at a given temperature was the most important influencing factor on the austenitizing characteristic combined with deformation. Moreover, the hot-rolled microstructure also had to be prepared in an optimal state because of its direct effect on the warm-rolled microstructure.

关键词: Warm-rolled ferrite/pearlite , null , null

Numerical Simulation Of Molten Pool And Control Strategy Of Kiss Point In A Twin-Roll Strip Casting Process

G.M. Cao , C.G. Li , Z.Y. Liu , D. Wu , G.D. Wang , X.H. Liu

金属学报(英文版)

Coupled turbulent flow, temperature fields of the twin-roll casting strip process were simulated by three-dimensional finite element method. Based on the heat balance calculation and using inverse methods between the simulations and real experiments, the relational models among casting speed, location, and coefficient of heat transfer between molten metal and rolls in different regions are given. In the simulation, the calculated surface temperatures are in good agreement with the measured values. An on-line model of kiss point is derived by simulations and the geometry of molten pool, corresponding control strategy is also proposed.

关键词: Twin-roll strip casting , null

MECHANICAL STABILIZATION OF DEFORMED AUSTENITE DURING CONTINUOUS COOLING TRANSFORMATION IN A C-Mn-Cr-Ni-Mo PLASTIC DIE STEEL

D.S. Liu , G.D. Wang , X.H. Liu and G.Z. Cui(The State Key Laboratory of Rolling and Automation , Northeastern University , Shenyang 110006 , China)

金属学报(英文版)

The influence of prior austenite deformed at different temperature on the subsequent continuous cooling bainitic transformation has been investigated in an C-Ma-Cr-Ni-Mo plastic die steel. The results show that the prior deformation in low temperature region of austenite retards significantly the bainitic transformation. For the same continuous cooling schedule, as austenite deformed at lower temperature, the quantity of the classical sheaf-like bainite becomes less. The present results show that severe deformation leads to mechanical stabilization of austenite and causes the difficulty of bainitic ferrite propagation into the austenite.

关键词: plastic die steel , null , null , null , null

SIMULATION OF THE TWIN ROLL STAINLESS STRIP CASTING PROCESS

Y.C. Miao , X.M. Zhang , G.D. Wang

金属学报(英文版)

The position of the solidification completed temperature of twin roll stainless strip casting process is very important to the quality of the casting strip. In order to control this position, the solidification completed temperature should be known at first.The present paper first simulated dendritic microsegregation under conditions of twin roll stainless strip casting, and got the relationship between the temperature and solid fraction of the mush zone. The temperatures such as ZDT (equal to the solidification completed temperature) and LIT (liquid impenetrable temperature), et al., also were obtained. Then by using the turbulent model, the flow and thermal fields of the pool of the twin roll stainless strip casting, and the speed and temperature fields of different casting speeds were given and also explained. The results are coincident with the experimental result. Combined with the results of these two simulations. the appropriated casting speed was found.

关键词: strip casting , null , null , null , null

INFLUENCE OF COLD ROLLING TECHNOLOGY ON TEXTURE EVOLUTION OF IF STEEL

J.X. Li , X.H. Liu , G.D. Wang

金属学报(英文版)

Two kinds of cold rolling experiments, single cold rolling and double cold rolling, werecarried out on one titanium stabilized interstitial free (IF) steel that has been warmrolled at ferrite temperature. The main aim was to investigate the evolution of rollingand annealing textures from the well known behavior observed under single cold rollingcondition to the less understood double cold rolling by using orientation distributionfunction (ODF). In the twice cold rolled samples, the annealing texture comprises onlyfirst round of rolling. Accordingly both the once cold rolled sample and the twice coldrolled sample with heavy reduction in the first round of rolling have much complextexture components. They are related to the formation of initial {111} subgrain andthe priority growth of stable {111} nucleus.

关键词: double rolling , null , null , null , null

SPIN-LATTICE COUPLING-COEFFICIENTS G(11) AND G(44) FOR 3D(5) IONS IN 12-FOLD CUBIC COORDINATION

Physica B-Condensed Matter

Similar to the cases of 3d(n) ions in 4-fold (or 8-fold) and 6-fold cubic coordinations, a simple and uniform method that calculates the spin-lattice coupling coefficients G11 and G44 for those ions in the more complex 12-fold cubic coordination from the derivatives of zero-field splittings in low symmetries with respect to the distinct structural parameters has been established. Through this method, the analytic expressions of G11 and G44 for 3d5 ions in this cubic coordination based on various mechanisms and models have been given. The results are rather different from those in 4-fold (or 8-fold) and 6-fold cubic coordinations. As an example, the coefficients G11 and G44 for Fe3+ in K+ site ( 12-fold cubic coordination) as well as Ta5+ site (6-fold cubic coordination) of KTaO3 crystal are studied from the important spin-orbit coupling mechanism. When we compare these results with the experimental findings, it appears that the Fe3+ ion is in a Ta5+ site, and not in a K+ site as shown by some researchers.

关键词: s-6-state ions;symmetry;formulas

Theoretical investigations of the local structures and the g factors for 3d(9) ions in CdS

Physics and Chemistry of Minerals

The local structures and the g factors g (//) and g (aSyen) for the isoelectronic 3d(9) ions Cu(2+) and Ni(+) in CdS are theoretically investigated from the perturbation formulas of these parameters for a 3d(9) ion under trigonally distorted tetrahedral environments. In consideration of significant covalency of the [MS(4)] combinations (M = Cu and Ni), the ligand orbital and spin-orbit coupling contributions are taken into account using the cluster approach. Based on the studies, the substitutional impurity Cu(2+) (or Ni(+)) on Cd(2+) site is found to undergo a small inward displacement 0.026 (or a slight outward shift 0.017 ) towards (or away from) the ligand triangle along C (3) axis. The theoretical g factors for both ions based on the above impurity displacements are in good agreement with the experimental data.

关键词: Electron paramagnetic resonance;Defect structures;Crystal-fields and;spin Hamiltonians;Cu(2+);Ni(+);CdS;electron-paramagnetic-resonance;atomic screening constants;defect;structures;crystal-field;3d impurities;scf functions;semiconductors;parameters;epr;spectra

Zero-field splitting and g factors for d(2) ions in trigonally distorted cubic crystal fields

Communications in Theoretical Physics

By successively taking into account various interactions for d(2) ions in trigonally distorted cubic crystal fields, detailed analyses, derivations and calculations of the zero-field splitting (ZFS) and g factors of the ground state have been carried out; and their physical essentials and origins have been clearly revealed. The mistakes and shortcomings in some references have been corrected and improved. The calculated results are in excellent agreement with experimental data and much better than those of previous work. It is found that both the combined action of the trigonal field and spin-orbit interaction and the interaction between the ground state and excited states are quite necessary for causing ZFS of the ground state, and both the spin-orbit interaction and the admixture between the ground state and excited states are necessary for causing the deviation of g factors of the ground state from spin-only values.

关键词: zero-field splitting;g factors;d(2) ions;crystal field;combined;action;admixture of wavefunction

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

Studies of EPR g factors of the isoelectronic 3d(3) series Cr3+Mn4+ and Fe5+ in SrTiO3 crystals

Journal of Physics and Chemistry of Solids

The g-shifts Ag( = g-g(s), where g(s) approximate to 2.0023 is the free-ion value) of the isoelectronic 3d(3) series Cr3+. Mn4+ and Fe5+ in SrTiO3 crystals are calculated from the high-order perturbation formula based on the cluster approach for 3d3 ion in cubic octahedral site. The formula includes not only the contribution from the crystal-field (CF) mechanism, but also that from the charge-transfer (CT) mechanism (which is omitted in the CF theory). From the calculations, it is found that the contribution Delta g(CT) from the CT mechanism in sign is contrary to the corresponding Delta g(CF) from the CF mechanism and the relative importance of CT mechanism (characterized by vertical bar Delta g(CT)/Delta g(CF)vertical bar) increases with the increasing valence state (and hence the atomic number) of 3d(3) ion. The positive g-shift Delta g of SrTiO3:Fe5+ is due mainly to the contribution of CT mechanism. So, for the explanations of g factors of the high valence state 3d" ions (e.g. Mn4+ and Fe5+) in crystals, the contributions from both CF and CT mechanisms should be taken into account. (c) 2005 Elsevier Ltd. All rights reserved.

关键词: oxides;crystal fields;electronic paramagnetic resonance;optical;properties;electron-paramagnetic-resonance;atomic screening constants;scf;functions;luminescence;parameters;spectra;temperature;manganese;lattices;csmgbr3

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