Competing Grain-Interior and Grain-Boundary Deformation Mechanisms in Nanocrystalline Materials and Thin Films

纳米晶材料和薄膜中相互竞争的晶界和晶界变形机制PI：高华健，布朗大学摘要本研究的目的是研究纳米晶材料和薄膜的力学性能，晶界和晶界变形机制之间存在强耦合。本研究将采用理论分析和数值计算相结合的方法(积分-微分方程法、基于有限元的介观模型、离散位错动力学和分子动力学方法)。这个项目将对一些基本问题进行系统的研究，包括100 nm或更小尺寸/膜厚的系统中晶界和晶内的竞争变形，纳米晶体材料和超薄膜中非均匀晶界扩散系数和滑动阻力的影响，晶界扩散和晶界滑动之间的相互作用以适应相容变形，以及具有表面和晶界扩散的薄膜的力学行为。这个项目将产生新的知识和基本的理解，可能为现代技术的广泛应用提供见解和指导方针，包括微电子和光电子的薄膜结构，MEMS器件，燃气轮机热障涂层，材料工程中的摩擦学涂层和纳米技术。该项目的教育部分包括培训一名博士生，指导本科生，并将最先进的研究成果吸收到布朗大学现有的工程学研究生和本科生课程中，目前该校的学生对纳米材料和结构的界面力学有浓厚的兴趣。更多的外展活动将由布朗？S材料研究科学与工程中心(MRSEC)协调进行，该中心已建立了一套优秀的外展教育项目。该奖项由CMMI-材料力学与结构和DMR-金属项目共同资助。

Competing Grain-Interior and Grain-Boundary Deformation Mechanisms in Nanocrystalline Materials and Thin FilmsPI: Huajian Gao, Brown UniversityAbstract The objective of this proposal is to investigate mechanical properties of nanocrystalline materials and thin films with strong coupling between grain boundary and grain interior deformation mechanisms. A combination of theoretical analysis and numerical techniques (integro-differential equation modeling, finite element based mesoscopic modeling, discrete dislocation dynamics and molecular dynamics methods) will be adopted in the study. A systematic investigation will be conducted on a number of fundamental issues including competing deformation in grain boundaries and grain-interiors in systems with grain sizes/film thicknesses on the order of 100 nm or smaller, effects of heterogeneous grain boundary diffusivity and sliding resistance in nanocrystalline materials and ultrathin films, interplay between grain boundary diffusion and grain boundary sliding to accommodate compatible deformation, and mechanical behaviors of thin films with surface and grain boundary diffusion.This project will generate new knowledge and fundamental understanding that may provide insights and guidelines for a wide range of applications in modern technologies including thin film structures in microelectronics and optoelectronics, MEMS devices, thermal barrier coatings in gas turbines, tribological coatings and nanotechnology of materials engineering. The educational components of the project include training of a PhD student, mentoring of undergraduates, and assimilation of state-of-the-art research results into the existing graduate and undergraduate courses in engineering at Brown where there are currently strong student interests in interfacial mechanics of nanoscale materials and structures. Additional outreach activities will be mediated by Brown?s Materials Research Science and Engineering Center (MRSEC) which has established a set of excellent outreach educational programs.This award is co-funded by CMMI - Mechanics & Structure of Materials and DMR-Metals programs.