Modeling and Design of Enhanced Strength and Ductility Through Grain Boundary Engineering--A Study of Boron Carbide Based Superhard Materials

强度是指材料承受失效或屈服的能力，而延展性是材料永久变形而不断裂的能力。许多重要的工程应用需要高强度和延展性的材料，例如切割工具，士兵防弹衣和制造过程。一种很有希望的候选者是碳化硼，一种所谓的超硬陶瓷，因其强度而得名；然而，它的延展性很低。在多晶材料中，强度和延展性通常与较低长度尺度（微米及以下）的微观结构特征有关。关于微观结构对超硬陶瓷的强度和延展性的影响，目前还存在很大的知识空白。该项目旨在通过计算建模和模拟，研究碳化硼基材料的微观结构、强度和延展性之间关系的物理机制。该项目还将根据所获得的知识建立设计原则，用于开发具有增强强度和延展性的新型碳化硼基材料。该设计策略将扩展到各种其他超硬材料，如硼化物、碳化物和金刚石。该研究将整合到本科和研究生教育中，并为当地高中生提供外展活动。该研究项目还将针对女性和代表性不足的少数民族学生参与科学、技术、工程和数学学科。本项目的研究目的是阐明微观结构如何决定碳化硼基材料的变形和力学过程。研究团队将采用多尺度方法耦合原子模拟和中尺度相场方法(1)研究晶界对碳化硼力学性能、变形和破坏机制的影响；(2)建立了通过微合金化晶界性能工程来提高碳化硼强度和塑性的设计原则。该研究将为揭示多晶超硬陶瓷在现实条件下强度和延展性的成因做出原创性贡献。材料设计原则将应用于激发实验合成更强和更坚韧的碳化硼基材料的商业应用。

Strength refers to a material's ability to withstand failure or yield, while ductility is its ability to permanently deform without fracture. Many important engineering applications require high strength and yet ductile materials, such as in cutting tools, body armor for soldiers, and manufacturing process. One promising candidate is boron carbide, a so-called superhard ceramic names so because of its strength; however, it has low ductility. In poly-crystalline materials, the strength and ductility are commonly associated with microstructural features at the lower length scales (micrometers and below). There is a significant knowledge gap regarding the impact of microstructure on the strength and ductility of superhard ceramics. This project is directed towards the study of the physical mechanisms that underlie the relationships between microstructure, and strength and ductility of boron carbide based materials using computational modeling and simulations. The project will also establish design principles based on the knowledge gained for the development of new boron carbide based materials with enhanced strength and ductility. The design strategies will be extendable to a variety of other superhard materials, such as borides, carbides, and diamond. The research will be integrated into both undergraduate and graduate education, as well as outreach activities for local high school students. The research project will also target the participation of women and under-represented minority students in science, technology, engineering, and math disciplines. The research objective of this project is to illustrate how microstructure determines the deformation and mechanical processes in boron carbide based materials. The research team will apply a multiscale approach coupling atomistic modeling and the mesoscale phase field method to (1) investigate the impact of grain boundaries on mechanical properties, deformation, and failure mechanisms of boron carbide; and (2) establish the design principles to enhance the strength and ductility of boron carbide through engineering of grain boundary properties with microalloying. The research will make original contributions in elucidating the origins of the strength and ductility of polycrystalline superhard ceramics under realistic conditions. The materials design principles will be applied to inspire experimental synthesis of stronger and tougher boron carbide based materials for commercial applications.