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摘要本文利用 Cahn-Hilliard 扩散方程来描述合金相分解，建立相场动力学模型。分别模拟了不同成分和温度，以及外加应变条件下的合金扩散偶元素扩散和微观组织演变。建立不同条件下合金扩散偶模型。 随扩散偶两侧合金浓度差增大，形成的界面越明显越光滑，相同时间内扩散的程度和扩散速率逐渐增大；温度升高，界面越平滑，扩散偶的扩散程度和扩散速率先增大后减小。弹性应变能对沉淀相颗粒形貌和取向有重要影响。无外加应变时颗粒形貌为圆形或椭圆形，无明显空间取向;考虑弹性应变能后，颗粒形貌为长条状，且沿弹性应变方向分布，界面处富集相更为粗大，且排列较为整齐，扩散偶界面更加明显。 59643
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毕业论文关键词：二元合金，弹性应变，扩散，相场模拟
Title The Interface Microstructure Evolution in Diffusion Couples under Elastic Strain
Abstract This paper use Cahn-Hilliard diffusion equation to describe the alloy phase decomposition, and build the establishment phase field dynamics model. Simulated the changes of microstructure and diffusion under different temperature , applied strain or not, as well as concentration in different alloy, build different alloy diffusion couple model. The result show that with the development of concentration difference alloy diffusion couple the interface become smoother, the extent of spread and diffusion rate increases. Higher the temperature, smoother the interface, and with the temperature increases, the degree of diffusion and diffusion couple diffusion rate firstly increased and then decreased. Elastic strain energy on particle morphology and orientation of the precipitates have a major impact. The morphology of particle is round or oval without strain applied, and no significant spatial orientation. After considering the elastic strain energy, the morphology of particle became long strips, meanwhile distribution along the elastic strain direction, the interface phase enrichment is more coarse, and arranged more orderly, more obvious the diffusion couple interface.
Keywords：Binary alloys, Elastic strain, Diffusion, Phase-field modeling
目 录
第一章 引言 ... 1
1.1 二元合金 .. 1
1.2 扩散机制及其影响机制 .. 2
1.2.1 基本扩散定律——菲克定律 .. 2
1.2.1.1 扩散第一定律 .. 2
1.2.3 影响扩散的因素 .. 4
1.2.3.1 扩散偶两侧浓度差对于扩散过程的影响 ... 4
1.2.3.2 温度对于扩散过程的影响... 4
1.2.3.3 外加应变对于扩散过程的影响 ... 4
1.3 相场模拟 .. 4
1.3.2 相场法微结构设计 .. 5
第二章 相场模型.. 7
2.1 模型的建立 .. 7
2.2 模型的数值化处理 .. 9
2.3 计算流程 .. 9
第三章 结果与讨论 ... 11
3.1 二元合金扩散偶的互扩散 12
3.1.1 温度对于互扩散的影响 12
3.1.2 浓度差对于互扩散的影响 16
3.2 弹性应变下二元合金扩散偶的互扩散 21
3.2.1 弹性应变二元合金不同温度下互扩散的组织形貌 . 21