Mesoscopic TDGL Model for Formation of Domain Structures in D019 Type Ordering

Ryuichiro Oguma; Syo Matsumura; Tetsuo Eguchi

doi:10.4028/www.scientific.net/SSP.172-174.602

Paper Titles

Microstructures of Cu-Alloyed Ductile Cast Iron Treated by Two-Step Austempering
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Sequential Phase Formation during Reactive Diffusion of a Nanometric-Thick Mn Film on Ge(111)
p.579

Thermal Stability of Athermal and Deformation Martensite in Ni27Ti2AlMoNb Steel
p.585

Order and Disorder in Ni-Pt Single Crystals
p.593

Mesoscopic TDGL Model for Formation of Domain Structures in D0₁₉ Type Ordering
p.602

Re-Examination of A1 → L1₀ Ordering: Generalized Bragg-Williams Model with Elastic Relaxation
p.608

Effect of Magnetism on Short-Range Order Formation in Fe-Si and Fe-Al Alloys
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Evidence of a Biphasic Domain in the UO₂-Nd₂O₃Diagram at Room Temperature: a Proof for a Miscibility Gap in UO₂-Nd₂O₃ Phase Diagram ?
p.624

Theoretical and Experimental Evidences of Sequential Phase Formation during Sub-Nanometric-Thick Film Reactive Diffusion
p.633

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Mesoscopic TDGL Model for Formation of Domain Structures in D0₁₉ Type Ordering

Abstract:

The present authors recently presented the time-dependent Ginzburg-Landau (TDGL) formulation for L1₂ type ordering process in binary alloys, taking into account the symmetrical relationships of these ordered phases. Extending the formulation, the authors have developed the TDGL model for microstructural evolution of D0₁₉ type ordering. The D0₁₉ structure based on hcp is divided into four equivalent sublattices. The site occupation probabilities are given as a function of three order parameters and a composition parameter. Multiple types of variants of the structures are represented by the order parameters. Mean-field free energies are defined in a form of Landau type expansion with the order parameters and the composition parameter. Interfacial energies due to local variations of degrees of order and composition are given in a gradient square approximation. Kinetic equations for time-evolution of the order parameters and the composition one are derived from the Ginzburg-Landau type potential consisting of the mean-field free energies and the interfacial energy terms. Three-dimensional numerical simulations based on the kinetic equations have been performed, and the domain structures obtained are compared with a TEM image of Cu₃Sn alloy.