微纳米尺度位错与晶界相互作用的理论和计算研究

项目名称： 微纳米尺度位错与晶界相互作用的理论和计算研究

项目编号： No.11302115

项目类型： 青年科学基金项目

立项/批准年度： 2014

项目学科： 数理科学和化学

项目作者： 柳占立

作者单位： 清华大学

项目金额： 30万元

中文摘要： 位错-晶界作用是控制微纳米尺度多晶材料强度和延性的关键要素。本项目将从原子、离散位错、连续介质三个层次研究位错-晶界相互作用机理，分析其对多晶材料强度和延性的影响。在原子尺度研究单个位错和界面相互作用机制，确定控制位错/晶界行为的主要因素，通过粗粒化方法提取位错和晶界反应的临界应力及反应后的Burgers矢量信息，用于亚微米尺度离散位错模拟；在此基础上发展新的离散位错模拟方法，准确求解各向异性界面处位错应力场，根据原子尺度信息处理位错和晶界的近程相互作用，并通过均匀化理论提取位移和塑性应变间断等界面参数，作为微米尺度研究的输入信息；进而在连续介质层次上发展考虑界面效应的高阶晶体塑性理论，根据离散位错输入信息在界面处提出高阶边界条件描述位错在界面处的堆积、透射等机理。最后应用扩展有限元来捕捉界面位移、塑性应变间断，求解高阶晶体塑性方程，研究位错界面相互作用对多晶材料塑性变形影响。

中文关键词： 位错；晶界；离散位错动力学；高阶晶体塑性理论；

英文摘要： The interactions between dislocations and grain boundaries play an important role in controlling the strength and ductility of polycrystalline metals at micro/nano scale. This project aims at investigating the mechanism of dislocation-grain boundary interactions across the scales: from the atomistic level via the level of discrete dislocations to the continuum level-coupled by means of proper scale transitions. First, the interactions between single dislocation and grain boundary will be studied on the atomistic scale at the greatest detail to find the key factors which control the dislocation/grain boundary behavior. The critical values of the local stress/energy and the Burgers vector information after reaction will be extracted to serve as the input for the study at upper discrete dislocation level. Then a new 3D discrete dislocation dynamics (DDD) method will be developed to calculate the stress field of dislocations near the anisotropic interface. The short range interactions between dislocation and grain boundary will be treated according to the atomistic information. The interface properties like displacement and traction jump will be obtained from interfacial computational homogenization method and will be passed to the study at the micrometer scale. Next, a higher-order crystal plasticity theory conside

英文关键词： dislocation；grain boundary；discrete dislocation dynamics；higher-order crystal plasticity theory；