Materials World Network: Collaborative Research: Modeling Ferroelastic Strain Glasses

这个俄亥俄州州立大学（OSU）、宾夕法尼亚大学（UPenn）、日本国家材料科学研究所（NIMS）将日本方面的临界实验与美国方面的多尺度建模和模拟相结合，以了解和预测点缺陷对马氏体相变热力学和引发与传播动力学影响的纳米级机制（MT）。在与日本的形状记忆合金和应变玻璃的加工、测试和表征的合作机构的合作中，美国的参与者解决了关于MT和点缺陷的影响的长期感兴趣的基本问题，例如什么样的基本缺陷和缺陷过程构成MT的最小单元，这些基本缺陷过程的激活途径和势垒能是什么，以及点缺陷如何修改它们。特别是，研究人员系统地探测随机点缺陷对多平面广义堆垛层错（MGSF）能量景观沿着最小能量路径（MEP）连接的母相晶格的马氏体相晶格和振动熵，它们共同构成的晶体自由能，取代现象学的朗道自由能的影响。一个新的微观相场模型的基础上的从头算能量和反应坐标理论的MTs将进行测试。 要开发的方法和途径是相当普遍的，适用于一个更大的一组剪切为主的过程，如在许多先进的合金系统中发现的位移扩散变换和有序合金的塑性变形过程中的剪切重排过程。所开发的计算工具将通过从项目网站免费下载的方式广泛传播。涉及研究生，博士后研究人员和教师交流的教育工作将注入材料科学和技术的前沿发展，并为学生课程提供广阔的国际视野。

This joint project between Ohio State University (OSU), the University of Pennsylvania (UPenn), and the National Institute for Materials Science (NIMS) in Japan combines critical experiments from the Japanese side with multi-scale modeling and simulation from the U.S. side to understand and predict the nanoscale mechanisms underlying the effects of point defects on the thermodynamics and initiation and propagation kinetics of martensitic transformations (MTs). In collaboration with the partner institution in Japan on processing, testing and characterization of shape memory alloys and strain glasses, the US participants address fundamental questions of long standing interest concerning MTs and the effects of point defects, such as what elementary defect and defect process constitute the smallest unit of MT, what the activation pathway and barrier energy of these elementary defect processes are, and how point defects modify them. In particular, the investigators systematically probe the effects of random point defects on the multi-plane generalized stacking fault (MGSF) energy landscape along the minimum energy pathway (MEP) connecting the parent phase lattice to the martensitic phase lattice and on the vibrational entropies, which together constitute the crystalline free energy that replaces the phenomenological Landau free energy. A new microscopic phase field model of MTs based on the ab initio energetics and a reaction-coordinate theory will be tested. The methodology and approach to be developed are rather general and applicable to a larger set of shear-dominated processes such as the displacive-diffusional transformations found in many advanced alloy systems and the shearing-reordering process during plastic deformation of ordered alloys. Computational tools developed will be disseminated widely through free download from the project website. The educational effort involving the exchange of graduate students, postdoctoral researchers and faculty will inject cutting-edge development in materials science and technology and provide a broad international perspective to the student curricula.