金属Mg中孪晶形核与生长、二次孪晶变体优选机制及过渡态构型的跨尺度研究

项目名称： 金属Mg中孪晶形核与生长、二次孪晶变体优选机制及过渡态构型的跨尺度研究

项目编号： No.51301094

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： 徐贲

作者单位： 清华大学

项目金额： 25万元

中文摘要： 镁（Mg）及镁合金是国家十二五计划优先发展的先进轻质结构材料，在航空航天关键部件上有着广泛的应用前景。Mg合金变形能力差是其产业化的最大障碍。虽然孪晶能显著增强Mg合金的变形能力，但在孪晶之间及孪晶与晶界的交截处易产生裂纹,且二次孪晶会引起较大的剪切应变局域化,影响材料的安全服役。因此只有在原子和介观尺度下系统地阐明位错与位错，位错与孪晶，孪晶与孪晶，孪晶与界面的相互作用机理之后，Mg合金才能在航空航天的关键部件得以安全的使用。本项目在原子和介观尺度下，以Mg及Mg合金中的一次及二次孪晶为研究对象，使用过渡态理论动态地描述孪晶形核和长大过程，利用相互耦合的分子动力学，动力学蒙特卡罗及相场方法来研究孪晶变体周围协调应变的分布，以及该分布对二次孪晶变体优选规律和一、二次孪晶长大的影响。充分理解其结构-性能的关系，实现变形过程中对组织结构的预测，并结合实验验证，改进加工工艺促进Mg合金的工业化生产应用。

中文关键词： 金属镁；孪晶；位错；界面；生长过程

英文摘要： Mg and Mg alloys are advanced light-weight structural materials which can be widely used in key components in aerospace industry, and are therefore regarded as one of the key materials in 12th Five Year Plan. Nevertheless, poor ability for deformation of Mg alloys largely hampers their wide applications in industry. Twins in Mg alloys greatly improve the deformability of the material，although twin-grain boundary (GB) and twin-twin boundary compatibility interactions frequently lead to crack initiation. Besides, Mg alloys in safety critical applications have to consider negative influence from shear strain localization introduced by secondary twinning. A fundamental gap in the understanding of Mg alloy deformation needs therefore to be addressed before Mg alloys' critical applications in industry, which relates to atomistic and mesoscopic description of dislocation-dislocation, dislocation-twin, twin-twin, and twin-GB interactions and their effects on strain hardening and damage initiation. This project is mainly focused on the atomistic/mesoscopic modeling of first/second order twins nucleation and growth using transition states theory. The distribution of strain compatibility in the proximity of twins will be studied using methodologies coupling MD， kinetic MC and phase field theory, and thus reveal the selecti

英文关键词： Magnisium；Twin；Dislocation；Grain Boundary；Growth