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The Solute Precipitation and Grow up with Considering Elastic Stress Field Was Investigated by Using Phase Field Method

Author: TianJunLong
Tutor: GaoYingJun
School: Guangxi University
Course: Condensed Matter Physics
Keywords: phase-field method elastic stress field dislocation precipitate
CLC: TB303
Type: Master's thesis
Year: 2011
Downloads: 49
Quote: 0
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Abstract


Phase-field method with pro founder physical thought, which don’t need to track the movement of the interface,has become one of important calculation method in materials science research.Be widely used in study of the material microstructure evolution.Such as:grain growth,phase transformation,ceramic sintering,solidification, spinodal decomposition,ferroelectric and ferromagnetic etc. There are obvious advantages to study the influence of the defects for the evolution of material microstructure. The disloaction and strain has a big effect on the evolution of materials microstructure and the macro properties of materials. So it will be great important practical significance for the evolution of material microstructure to study the strain energy and dislocation. In order to reveal the impact of stress field,dislocation and dislocation group on the second phase precipitation evolution, this paper adopts phase-field method to study the influence of strain energy which produced by lattice distortions due to the dislocation and dislocation group for the morphology evolution of the second phase precipitation; What have been studied is the effect of elastic strain energy due to the lattice mismatch for the morphology evolution of the second phase precipitation in the process of spinodal decomposition. The main conclusions and innovations are as follows:1. Through studying the morphology evolution of the second phase precipitate with impacting of elastic strain field due to lattice mismatch,put forward the elastic strain energy with the interaction of the first power of the concentration field and the elastic stress field,explain that there was a great influence for the second phase precipitate in spinodal decomposition with the impact of elastic stress field.2. The edge dislocation can induce the second phase to nucleation and grow up and prompte the second phase to precipitate not considering thermodynamic disturbance;When existing the edge dislocation, the second phase precipitate at the underside of the positive edge dislocation where exist tensile stress of dislocation;Solute is depleted at the upside of the positive edge dislocation where exist compressive stress of edge dislocation.3. Detailed simulation the second phase precipitate evolution and revealed the regularity and mechanism of the second phase precipitation evolution when exist edge dislocation group:the morphology of the second phase precitation,nucleation and grow up at each edge dislocation is affected by the combined action of each edge dislocation and do not only depend on the edge dislocation where the second phase precipitate; the second precitation and nucleation is limited at the upside of the positive edge dislocation.So according to different dislocation configuration which can precipitate different morphology precipitation phase.4.Revealed the diffusion rule of the solute atoms in the process of the second phase nuclear,precipitate and grow up which is induced by edge dislocation or edge dislocation group:first of all,happened short-range diffusion near the line of edge dislocation;Then it also happened long-distance diffusion along with time evolution.Prompted the second phase nuclear,precipitate and grow up.This paper establishes a free energy function with the interaction of the concentration field and the elastic strain field. To study the influence of the elastic strain field due to different edge dislocation group on solute precipitation. Revealed the morphology characteristic and the diffusion law of the solute precipitation reasonably. It not only has high theoretical significance but also high practical significance.It can guide to design new material very well and study physical properties of material.

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