Twin Nucleation and Migration - Modeling and Experiments

双成核和迁移 - 建模和实验

• 批准号: 1130031
• 负责人: Huseyin Sehitoglu
• 金额: $ 27.48万
• 依托单位: University of Illinois at Urbana-Champaign
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-01 至 2015-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1130031&HistoricalAwards=false
• 关键词: Twin; Nucleation; Migration; Modeling; Experiments

This project is aimed at developing a hierarchical methodology for advanced materials design utilizing the most advanced first principles/mesomechanics tools combined with experiments. We plan to focus on bcc alloys such as Fe-Cr, Fe-Cr-Co and austenitic B2 shape memory alloys to develop our sequential multi-scale design approach. These alloys are of significant interest, but there has been no attempt to develop models to predict their deformation response from first principles. The deformation behavior of these alloys is characterized by significant twinning activity. A continuum twin nucleation model based on first-principle calculations will be developed. The research will determine how the energy barriers evolve and establish twin nucleation and twin migration stress levels, through consideration of the entire energy barrier transients, by carefully defining nucleation and migration phenomena. It is envisaged that confirmation of the model validity at the corresponding length scale by precisely measuring the local deformations associated with twinning including the twin shear strain. Observations of deformation are made at both the macro- and micro- levels using digital imaging techniques at multiple magnifications.The broad impact of the work is that our methodology will accelerate the design of advanced structural materials by avoiding the large test matrix approach and optimization trials. The mechanical response of bcc alloys have been predicted based on crystal plasticity models, which rely on a large number of experimentally determined constants. Overall, the emphasis on first principles/mesoscale mechanics combined with experiments is unique. In addition, there will be several outreach activities ranging from short courses to industry and advanced researchers, to learning modules with activity kits for K-12 students and their teachers, which will broaden the educational impact of the approach.

这个项目的目的是利用最先进的第一原理/细观力学工具和实验相结合，开发一种先进材料设计的分层方法。我们计划将重点放在体心立方合金，如Fe-Cr，Fe-Cr-Co和奥氏体型B2形状记忆合金，以发展我们的顺序多尺度设计方法。人们对这些合金很感兴趣，但还没有人尝试开发模型来根据第一性原理来预测它们的变形响应。这些合金的变形行为以显著的孪晶活动为特征。建立了一个基于第一性原理计算的连续孪晶成核模型。这项研究将通过仔细定义成核和迁移现象，通过考虑整个能垒的瞬变过程，确定能垒如何演变，并建立孪生成核和孪生迁移应力水平。设想通过精确测量与孪生有关的局部变形，包括孪生剪切应变，在相应的长度尺度上确认模型的有效性。利用数字成像技术在宏观和微观两个层面上对变形进行观测。这项工作的广泛影响是，我们的方法将通过避免大型测试矩阵方法和优化试验来加快先进结构材料的设计。基于晶体塑性模型对体心立方合金的力学响应进行了预测，该模型依赖于大量实验测定的常数。总体而言，强调第一原理/中尺度力学与实验相结合是独一无二的。此外，还将开展几项外联活动，从短期课程到工业和高级研究人员，再到为K-12学生及其教师提供活动包的学习单元，这将扩大这一方法的教育影响。