Grain Stability in Nanostructured Metals

本项目主要研究面心立方和六方密排晶体结构的金属以及含有或同时含有纳米颗粒或纳米孪晶的金属中超细颗粒和纳米结构颗粒的稳定性。纳米孪晶铜和纳米晶尺寸的钛将使用各种方法进行研究，包括微压痕、动态变形和微拉伸测试。钛的动态变形是专门用来记录钛晶界迁移导致超细晶结构不稳定的趋势的。补充的理论研究将包括使用我们新开发的有限温度准连续统方法的原子模拟。在这些研究中，将通过模拟纳米孪晶结构的形变来探索位错与孪晶的相互作用以及孪晶界的潜在运动(即不稳定性)。教育活动包括从代表性不足的群体中挑选出的研究生和本科生的培训；两名这样的本科生已经在研究直接相关的主题。建立了一个网站，以迅速传播新的结果，并充当其他人添加新获得的数据的储存库。我们正在参加一个名为“通往未来的桥梁”的项目，这是一个圣地亚哥的项目，旨在将未被充分代表的少数群体的职业生涯转变为科学。我们还参加了加州州立数学与科学暑期学校(COSMOS)，该学校面向对数学和科学表现出兴趣的9-12年级学生。我们在这方面的重点将是纳米技术。

Grain Stability in Nanostructured MetalsAbstractThis project is concerned with fundamental studies of the stability of ultra-fine and nanstructured grains in metals, both with face centered cubic and hexagonal close packed crystal structures, and in metals that contain either, or both, nano-sized grains or nano-sized twins. Nano-twinned copper and nano-grain size titanium will be studied using a variety of methods, including micro-indentation, dynamic deformation, and micro-tensile testing. The dynamic deformation in titanium is designed specifically to document the tendency of titanium grain boundaries to migrate leading to instability of the ultra-fine grain structure. Complimentary theoretical studies will include atomistic simulation using our newly developed finite temperature quasi-continuum method. In these studies simulations of the deformation of nano-sized twinned structures will be performed to explore the interaction of dislocations with twins and the potential motion (that is the instability) of twin boundaries.Educational activities include the training of graduate students and undergraduate students chosen from under represented groups; two such undergraduate students are already working on directly related topics. A web site is established to rapidly disseminate novel results and to act as a repository for others to add newly obtained data. We are participating in a program called ?Bridges to the Future?, a San Diego program designed to transition the careers of under represented minorities into science. We also participate in the California State Summer School for Mathematics and Science (COSMOS) aimed at 9th-12th graders who demonstrate interest in math and science. Our focus in this will be nanotechnology.