Collaborative Research: Computational and Experimental Study of Alloying Effects on <c+a> slip in Mg

非技术总结：由于其低密度，镁（Mg）和富镁合金在轻量化汽车技术中具有重要意义。然而，在环境温度下将这些材料形成有用形状的能力一直是广泛实施的致命弱点。室温成形性和损伤容限是镁合金在成本上与铝合金和钢具有竞争力的关键。这些特性依赖于易塑性变形，这是一种由原子水平过程介导的现象。这项研究工作为如何通过添加合金元素来促进提高成形性的原子过程提供了一个基本的理解。此外，与基于试错的传统经验方法相比，该计划开发的综合计算/实验方法是迈向基于物理的预测合金设计的关键一步，并且可以应用于具有类似晶体结构的一系列其他金属系统，例如技术上重要的Ti和Zr合金。此外，该计划的教育和推广部分旨在(1)将计算建模纳入课堂，以加强对困难概念的学习；(2)为材料科学和工程专业的学生准备未来的职业生涯，提高计算建模的重要性；(3)培养学生对科学、技术工程和数学（STEM）领域的热情，特别是来自代表性不足的群体。这个项目有一个与俄亥俄州立大学工程学院合作的外展项目组成部分。技术概述：本项目的首要目标是提高镁合金的室温变形能力。为了实现上述目标，本项目旨在通过有利的合金化激活c+a滑移模式。c+a位错核的电子结构计算将用于(1)确定稳定c+a边位错核几何形状的溶质(2)研究候选元素对c+a螺位错稳定性和交叉滑移率的影响。促进边缘段滑动而不影响螺钉段运动的元件将被建议为可行的候选元件。将通过实验(3)制备合金单晶(4)测量应力-应变曲线(5)表征位错结构演变来评估理论合金化建议的结果。该结果将为溶质对Mg中非基底变形模式激活的影响提供新的理解，从而可以提高Mg合金的室温延展性，从而增加这些轻质合金的广泛使用。

Nontechnical Summary:By virtue of their low density, Magnesium (Mg) and Mg-rich alloys are of significant interest in lightweight vehicle technology. However the ability to form these materials into useful shapes at ambient temperature has been the Achilles heel to widespread implementation. The room temperature formability and damage tolerance are essential to making the cost of Mg alloys competitive with those of aluminum alloys and steels. These properties rely on the ease of plastic deformation, a phenomenon that is mediated by atomic level processes. This research effort provides a fundamental understanding of how the atomic processes, responsible for enhanced formability, can be facilitated through addition of alloying elements. Furthermore, the integrated computational/experimental methodology developed by this program is a crucial step towards physics-based predictive alloy design compared to the traditional empirical approach based on trial and error and can be applied to a range of other metallic systems with similar crystal structure, such as technologically important Ti and Zr alloys. Moreover, the education and outreach component of this program, are aimed at (1) incorporating computational modeling in classroom to enhance learning of difficult concepts, (2) preparing materials science and engineering students for future careers with an increased importance of computational modeling and (3) fostering enthusiasm about Science, Technology Engineering and Math (STEM) fields in students, particularly from underrepresented groups. This project has an outreach program component in collaboration with the college of Engineering at the Ohio State University.Technical Summary:The overarching goal of this program is to enhance the room temperature deformability of Mg alloys. In pursuit of the above goal, this project aims to activate the c+a slip mode through favorable alloying. Electronic-structure calculations of c+a dislocation cores will be used to (1) Identify solutes that would stabilize the glissile core geometry of the c+a edge dislocations (2) Study the effect of candidate elements on the stability and cross-slip rate of c+a screw dislocations. Elements that promote the slip of edge segments without compromising the motion of screw segments will be suggested as viable candidates. The consequence of the theoretical alloying suggestions will be evaluated experimentally by (3) making single crystals of the proposed alloys (4) measuring stress-strain curves and (5) characterizing dislocation structure evolution. The outcome will provide new understanding of solute effects on easier activation of non-basal deformation modes in Mg that can then enhance room temperature ductility of Mg alloys, thereby increasing the widespread use of these lightweight alloys.