铝中形变孪晶形成临界条件的多尺度模拟研究

项目名称： 铝中形变孪晶形成临界条件的多尺度模拟研究

项目编号： No.51301035

项目类型： 青年科学基金项目

立项/批准年度： 2014

项目学科： 一般工业技术

项目作者： 金剑锋

作者单位： 东北大学

项目金额： 25万元

中文摘要： 传统实验下晶粒粗化的纯铝中，塑性变形的机制只包含位错滑移而没有形变孪晶；而在纳米晶下，塑性变形机制可以是形变孪晶。由此表明铝中形变孪晶的产生带有明显的晶界尺寸效应。结合之前的科研成果，即在控制加载方式来限制全位错产生的条件下，通过相同肖克莱不全位错并排产生、滑移、层错重叠的机制形成形变孪晶；其原因为形成非并排不全位错的能垒高于形成并排不全位错的能垒。本次申请的课题，将运用多尺度准连续模拟结合分子动力学的方法，深入研究晶粒尺寸、形状、取向、加载方式对全位错形成的限制能力，进而得出形变孪晶形成的临界条件；最后希望本次研究成果可以更好的控制在实验条件下产生铝孪晶结构，扩展理解低维纳米结构材料中独特的变形机制。

中文关键词： 准连续方法；纳米微凸体；纳米孔洞；初始塑性；尺寸效应

英文摘要： Traditional experimental results proved that coarse-grain pure aluminum (Al) cannot form deformation twins, only dislocation slip. However, recently, nanocrystalline Al has been detected to form deformation twinning during plastic deformation. Therefore, deformation twinning shows a strong size effect. My previous simulation results provide a theoretical support, that is, if a full dislocation generation has been restricted under a certain loading condition, it is possible to form deformation twins by overlapping stacking faults in neighboring parallel partial dislocations with the same Burgers vector；because the energy barrier to form unparallel partial dislocations is higher than that to parallel ones. In this project, using multiscale quasicontiuum and molecular dynamics methods, we will give an in-depth investigation to the mechanism of deformation twinning associated with grain size, shape，orientation and loading condition to identify a critical condition of twin formation, which would lead us to control deformation twinning formation and better understand nanostructrual materials.

英文关键词： quasicontinuum method；nano-scale asperity；nanocavity；onset plasticity；size effect