摘要：为了从原子尺度了解BCC金属中位错与晶界的交互作用，以纯W为研究对象，基于分子动力学方法，实施了计算机模拟研究。文中简要叙述了分子动力学方法，经典的势函数模型，解理断裂能，同时简要介绍了位错理论知识，如位错分类，柏氏矢量，位错运动等。对模拟结果进行了分析，得到以下结论：(1)在拉伸初期，呈现弹性变形特点，之后晶界处形成孪晶，发生塑性变形；(2)位错在应力作用下逐渐向晶界方向运动，并被晶界吸收，然后在另一半晶体中激发出不同滑移面和滑移方向上的位错发射，同时晶界处会有残留位错的产生，以保证前后过程的柏氏矢量平衡；(3)施加应力于晶粒，会产生大量位错，位错逐渐运动，塞积于晶界，晶界能升高，之后晶界发射位错，晶界能逐渐恢复稳定。26056
关键字 位错 晶界 分子动力学 解理断裂能
毕业论文设计说明书外文摘要
Title The interaction between grain boundaries and dislocations in pure tungsten
Abstract
To understand the interaction of dislocations and grain boundaries in BCC metal at atomic-level, a computer simulation study was carried out based on molecular dynamics method. In this work we take tungsten as research object. Molecular dynamics method, besides classical potential models and cleavage fracture energy are introduced briefly. And some simple dislocation theory is also described, such as the category of dislocation, the Burgers vector as well as dislocation motion. From the simulation results，The following results are obtained: (1) At the beginning of the process of tension, the elastic deformation is characterized, and twin grains are formed at grain boundary, the plastic deformation occurs; (2) Dislocations move in the direction of grain boundary under applied stress gradually, and been absorbed. And then in the other half of the crystal stimulate dislocation emission of different slip plane and slip direction, the grain boundaries at the same time produce residual dislocation, to ensure the Burgers vector before and after are equilibrium; (3) The applied shear stress makes the dislocation to move gradually to the grain boundary and the energy increases, then the grain boundary stabilized gradually after the dislocation emission.
Keywords dislocation grain boundary molecular dynamics cleavage fracture energy
目 次
1 绪论 1
1.1 课题研究目的及意义 1
1.2 晶体的晶界模型 2
1.2.1 晶体的界面结构 2
1.2.2 晶界对材料的影响 2
1.2.3 重合位置点阵（CSL模型） 2
1.3 位错 3
1.3.1 刃型位错 4
1.3.2 螺位错 4
1.3.3 柏氏矢量 5
1.4 国内外研究情况 6
2 分子动力学方法 8
2.1 基本原理 8
2.2 边界条件 8
2.3 基本方程式 9
2.4 MD模拟的基本步骤 11
3 势函数的选取 12
3.1 常见势函数模型 12
3.2 纯W的势函数 14
4 晶界模型建立及能量计算 15
4.1 模型建立 15
4.2 能量的计算 18
4.2.1 内聚能 18
4.2.2 晶界能 19
4.2.3 模拟拉伸和晶界解理断裂能 20
5 位错与晶界相互作用分子动力学模拟 25 纯W中位错与晶界相互作用机制研究:http://www.youerw.com/cailiao/lunwen_20094.html