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Theoretical Analysis of Lattice Parameter Effect on order-disorder transformation Based on Pair Potential

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Journal of University of Science and Technology Beijing 2002年第1期9卷 53-58页

作者： TimotheeNsongo XiaodongNi StateKeyLaboratoryforAdvancedMetalsandMaterials.UniversityofScienceandTechnologyBeijing Beijing100083China AppliedScienceSchool UniversityofScienceandTechnologyBeijingBeijing1

Based on pair potential, the Bragg Williams (B-W) model is modified to takeinto account the effect of the lattice parameter on theoretical order-disorder transformationanalysis. The main purpose of this work is to understand the basic aspects of this effect andrelated reasonable model on order-disorder transformation. In the present approach, theconfiguration free energy is chosen as function of the lattice parameter and the long-range *** energy is calculated through Taylor's expansion, starting from the disordered state. It wasfound that the configuration free energy has been strongly modified when the lattice parameter istaken into account. It was also found only one type of order-disorder transformation exists in ABalloy and three kinds of order-disorder transformations for non-equiatomic alloy system such as A_3Balloy. This result is in agreement with experiments.

关键词： order-disorder transformation computer simulation pair potential phasetransformation

EAM Analysis of the Lattice Parameter Effect in order-disorder transformation

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Journal of University of Science and Technology Beijing 2001年第3期8卷 189-194页

作者： Timoth■e Nsongo, Xiaodong Ni, Guoliang Chen State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, China Faculty of Science, Physics Department, P. O. Box 69, Brazzaville (CONGO) Applied Scie State Key Lab. for Adv. Met. Mat. Univ. of Sci. and Technol. Beijing Beijing 100083 China

The embedded atom method (EAM) was used to theoretically analyze the effect of the lattice parameter variation on the order-disorder transformation in binary alloys. Based on EAM, it is found that only one kind of order-disorder transition (second-order transition) exists for AB alloy. Three groups of order-disorder transformation can be observed for the A(3)B or AB(3) compounds. For group I, the order-disorder is a completely first-order transition. For group II, the order-disorder transformation is a classical first-order transition. For group III, the order-disorder transformation is found to be a second-order transition. The lattice parameter variations have a significant effect on E-2 coefficient, which is related to the ordering energy. These results are in good agreement with experiments.

关键词： order-disorder transformation embedded atom method (EAM) phase transformation binary alloy

Influence of Aluminum Content in γ-TiAl with L1_0 Structure during ordering Processes

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Rare Metals 2001年第4期20卷 230-235页

作者： Timothée Nsongot1,2 Xiaodong Ni1,3 Guoliang Chen1, Keh-Minn Chang4 1) State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, China 2) Faculty of Science, P. 0. Box 69, Brazzaville, Congo 北京科技大学新金属材料国家重点实验室北京 100083 West-Virginia University 美国

Based on EAM (embedded atom method) interatomic potential, the effect of aluminum content on the type of order-disorder transformation (ODT) and the structure properties (lattice constants, volume, c/a ratio and configu- ration energy) during ordering processes was investigated for γ-TiAI based alloys. Results show that for the alloys with lower than 50%Al (all composition is in atom number fraction), the ODT is the first order transition, and the second order transition for the alloys with equal or higher than 50% Al. The increase of aluminum content results in the critical temperature increasing. The aluminum content has a very little effect on the lattice constants, the volume and the c/a ratio, but has a significant effect on the configuration energy. A metastable disordered state was found for the alloys with less than 50%Al.

关键词： TiA1 order-disorder transformation long-range order

RELATIONSHIP OF STRUCTURAL STABILITY AND LONG-RANGE-order PARAMETER FOR STOICHIOMETRY NiAI

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International Journal of Minerals,Metallurgy and Materials 1996年第2期10卷 79+75-79页

作者：倪晓东王西涛陈国良北京科技大学新金属材料国家重点实验室

The relationship between the structural stability and the long-range-order parameter of stoichiometry NiAl has been studied using effective atom model based on the embedded-atom-method(EAM) potential. The results obtained from the computation show that NiAl lacks a metastable disordered structure intrinsically, and has the stable ordered B2 phase,which are consistent with experimental results.

关键词： NiAl intermetallic computer simulation order-disorder transformation