Nanoscaled deformation and fracture processes in nanolayers

由两种或两种以上材料组成的亚微米级多层材料在许多工业领域的高科技应用和器件中具有重要意义，包括微电子、磁记录、光学和微机电系统。这些器件的物理性能和可靠性取决于多层材料的结构完整性。因此，在世界范围内对多层材料的力学响应，包括变形和断裂行为有相当大的研究兴趣。基于这些先进的多层系统开发可行的新型设备及其进一步改进，需要对宏观变形和断裂性能的基本过程有基本的了解。该项目的主要目标是通过动态原位应变TEM实验和静态死后TEM实验来研究精心挑选的纳米级多层材料模型断裂的微塑性过程。这项研究将对多层材料中位错的迁移率、与界面的相互作用及其与裂纹扩展的关系产生新的见解。因此，将阐明Cu/Ni、Cu/Cr和Cu/TiN多层材料在选择界面结构和层厚时的塑性、局部流动和断裂过程之间的基本关系。项目目标：利用原位应变透射电镜研究金属/金属（Cu/Ni, Cu/Cr）和金属/陶瓷（Cu/TiN）多层材料的变形和断裂过程。利用位错-界面相互作用模型预测纳米层的抗断裂能力和界面对裂纹尖端应力的影响，并将其作为层厚度和晶体取向的函数。将进行原位TEM断裂实验和基于位错的纳米层变形和断裂过程建模。项目将对两名研究生（材料科学和机械工程专业各一名）进行如下培训：学生1：纳米层微塑性和断裂的原位TEM实验（Wizorek博士）；学生2：基于位错的变形和断裂过程建模（Mao博士）。Mao将负责设计原位应变实验和基于位错的建模。Wiezorek博士将负责TEM表征和原位TEM测试的性能。由于所提出的研究具有综合性和跨学科的性质，学生的参与将为新世纪培养新一代材料科学家提供有效的手段。

0140317MaoNanoscale multilayers, composed of sub-micrometer thick layers of two or more species of materials are of significant interest for high-technology applications and devices in many fields of industry, including microelectronics, magnetic recording, optics, and micro-electro-mechanical systems. The physical performance and reliability of these devices depend on the structural integrity of the multilayers. Hence, there is considerable worldwide research interest in the mechanical response of multilayers, including the deformation and fracture behavior. The development of viable novel devices based on these advanced multilayer systems and their further improvement requires a basic understanding of the fundamental processes that are the agents of the macroscopic deformation and fracture performance. The main goal of the proposed project is the investigation of the processes of micro-plasticity involved in the fracture of carefully selected model nanoscale multilayer systems by dynamic in-situ straining TEM experiments as well as static post-mortem TEM. This research will produce new insights regarding dislocation mobilities and interactions with interfaces and their relationship to crack growth in multilayers. Hence, the fundamental relationships between processes of plasticity, local flow and fracture in Cu/Ni, Cu/Cr and Cu/TiN multilayers with selected interfacial structure and layer thickness will be elucidated. The project objectives are:to investigate the deformation and fracture process of metal/metal (Cu/Ni, Cu/Cr) and metal/ceramic (Cu/TiN) multilayers by in-situ straining transmission electron microscopy. to predict the fracture resistance and the effect of interfaces on crack tip stresses in the nanolayers as a function of layer thickness, and crystal orientation using a dislocation-interface interaction model.Both in-situ TEM fracture experiments and dislocation based modeling of the deformation and fracture processes in the nanolayers will be performed. Two graduate students (one in materials science and one in mechanical engineering) will be trained during the project as the follows: Student 1: in-situ TEM experiment on microplasticity and fracture in nanolayers (Dr. Wizorek)Student 2: dislocation based modelling on the deformation and fracture process (Dr. Mao).Dr. Mao will be responsible for the design of the in-situ straining experiments and dislocation-based modeling. Dr. Wiezorek will be responsible for the performance of TEM characterization and in-situ TEM testing. Because of the comprehensive and interdisciplinary nature of the proposed research, the involvement of students in the project will provide effective means for training of the new generation of materials scientists for the new century.