Materials World Network: Collaborative Research: Modeling Ferroelastic Strain Glasses

俄亥俄州立大学(OSU)、宾夕法尼亚大学(UPenn)和日本国家材料科学研究所(NIMS)的这一联合项目将日方的关键实验与美方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(MTS)热力学和引发和传播动力学的影响的纳米级机制。在形状记忆合金和应变玻璃的加工、测试和表征方面，美国与会者与日本的合作机构合作，解决了与MTS有关的长期感兴趣的基本问题和点缺陷的影响，例如，什么元素缺陷和缺陷过程构成了MT的最小单位，这些元素缺陷过程的激活路径和势垒能是什么，以及点缺陷如何改变它们。特别是，研究人员系统地探索了随机点缺陷对连接母相晶格和马氏体相晶格的最小能量路径(MEP)上的多平面广义堆积层错(MGSF)能谱和振动熵的影响，这些效应共同构成了取代唯象朗道自由能的晶体自由能。基于从头算能量学和反应配位理论建立了一种新的MTS微观相场模型。所研究的方法和途径具有一定的通用性，适用于更大范围的剪切主导过程，如许多先进合金体系中的位移-扩散相变和有序合金塑性变形过程中的剪切-再有序过程。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努力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角。

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.