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Study on Modification Mechanism of Rare Earth in ZA27 Cast Alloy with Electronic Theory and Molecular Dynamics method

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Journal of Materials Science & Technology 2004年第5期20卷 586-588页

作者： Guili LIU, Rongde LI and Zhenping ZHOUSchool of Materials Science and Engineering, Shenyang University of Technology, Shenyang 110023, China Sch. of Mat. Sci. and Eng. Shenyang Univ. of Technol. Shenyang 110023 China

A model of liquid ZA27 cast alloy is established according to molecular dynamics theory and an atomic structural model of co-existent a phase and liquid is also presented by means of computer programming. recursion method is adopted to calculate the electronic structure of RE (rare earth) in grains and around phase boundaries respectively. The calculation shows that RE is more stable around phase boundaries than in grains, which explains the fact that the solution of RE in a phase is less, and RE mainly aggregates in front of phase boundary. The calculations of bonding order integrals also show that RE in front of phases hardly solidify onto the grain surfaces as active element so as to prevent grains growth and refine the grains. As a result, the modification mechanism of RE may be explained from the view of electronic structure.

关键词： Atomic structural model recursion method Electronic structure Modification mechanism Rare easth

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Electronic Theoretical Study of the Interaction between Rare Earth Elements and Impurities at Grain Boundaries in Steel

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Journal of Rare Earths 2003年第3期21卷 372-374页

作者：刘贵立张国英李荣德 Materials Science and Engineering College Shenyang University of Technology

The model of dislocations was used to construct the model of grain boundary (GB) with pure rare earths, and rare earth elements and impurities. The influence of the interaction between rare earth elements and impurities on the cohesive properties of 5.3° low angle GB of Fe was investigated by the recursion method. The calculated results of environment sensitive embeding energy( E ESE ) show that the preferential segregation of rare earth elements towards GBs exists. Calculations of bond order integrals (BOI) show that rare earth elements increase the cohesive strength of low angle GB, and impurities such as S, P weaken the intergranular cohesion of the GB. So rare earth element of proper quantity added in steel not only cleanses other harmful impurities off the GBs, but also enhances the intergranular cohesion. This elucidates the action mechanism of rare earth elements in steel from electronic level and offers theoretical evidence for applications of rare earth elements in steels.

关键词： metal material grain boundary recursion method impurities the interaction between rare earth elements and impurities rare earths

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Modification Mechanism of Rare Earth Elements in ZA27 Casting Alloys

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Journal of Rare Earths 2003年第6期21卷 660-663页

作者：刘贵立李荣德 College of Materials Science and Engineering Shenyang University of Technology

The model of the liquid-phase ZA27 alloys was set up by molecular dynamics theory. The atomic structure of phase, RE-compounds, and the phase-liquid interface in ZA27 alloys were constructed by computer programming. Electronic structures of phase with rare earth elements dissolved and of phase-liquid interfaces with rare earth elements enrichment in ZA27 casting alloys were investigated by using the recursion method. The ESE energy of RE elements and the structure energy of RE-compounds, phase, and the liquid-phase ZA27 alloys were calculated. The results show that rare earth elements are more stable to be in the phase interface than in phase, which explains the fact of very small solid solubility of rare earth elements in phase, and the enrichment in the solid-liquid growth front. This makes dendrite melt and break down, dissociate and propagate. RE-compounds can act as heterogeneous nuclei for phase, leading to phase refinement. All above elucidates the modification mechanism of rare earth elements in zinc-aluminum casting alloys at electronic level.

关键词： metal materials atomic structure model recursion method electronic structure modification mechanism rare earths

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Research of the behaviour of O chemisorption on the （110） surface of Rhx-Pt1-x alloy

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Chinese Physics B 2006年第3期15卷 641-644页

作者：张辉张国英王瑞丹钟博 College of Physical Science and Technology Shenyang Normal University Shenyang 110034 China

An atomic group model of the disordered binary alloy Rhx-Pt1-x has been constructed to investigate surface segregation. According to the model, we have calculated the electronic structure of the Rhx-Pt1-x alloy surface by using the recursion method when O atoms are adsorbed on the Rhx-Pt1-x （110） surface under the condition of coverage 0.5. The calculation results indicate that the chemical adsorption of O changes greatly the density of states near the Fermi level, and the surface segregation exhibits a reversal behaviour. In addition, when x 〈 0.3, the surface on which O is adsorbed displays the property of Pt; whereas when x 〉 0.3 it displays the property of Rh.

关键词： chemisorption surface segregation recursion method density of states

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