Nanoscaled deformation and fracture processes in nanolayers

University Of Pittsburgh, Pittsburgh PA

Investigators

Abstract

0140317 Mao Nanoscale 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.