The Influence of 3D Interfaces on Mechanical Behavior of Nanolaminated Bimetallic Composites

Abstract

Cu/Nb nanolaminates containing 3D interfaces (3D Cu/Nb) are used in this study to demonstrate the effects of controlled interface structure on mechanical behavior and unit deformation activity in nanostructured alloys. 3D interfaces are internal boundaries that exist on length scales relevant to unit deformation mechanisms and contain nanoscale chemical and crystallographic heterogeneities in all spatial dimensions. 3D interfaces are a new method to manipulate alloy microstructure whose effects on plastic deformation have not been previously explored in depth. Elucidation of the link between 3D interface structure and mechanical behavior will provide key insights into nanoscale metallic deformation allowing for materials that exhibit near-theoretical strengths while also being highly deformable. The exploration of these themes requires understanding of a wide range of topics in physical metallurgy, which is reflected in the structure of this thesis. Chapter 1 begins with a high-level overview of the motivation and methodology of this work. Chapters 2 introduces fundamental concepts of metallic deformation at the macroscale and the atomic scale. Chapter 3 explores the participation and influence of interfaces in atomic scale deformation and ties the nanoscale to the mesoscale by discussing previous findings about atomically sharp 2D interfaces on nanocrystalline alloy mechanical behavior. Chapter 4 introduces the experimental methods required to characterize 3D interfaces structurally and mechanically. Chapter 5 presents structural characterization results, while Chapter 6 presents mechanical characterization results. Chapter 6 contains findings from mechanical testing, while also providing discussion connecting 3D interface structure detailed in Chapter 5 to observed 3D Cu/Nb mechanical behavior. The information from these techniques are crucial to forming structure-behavior relationships detailing the effect of 3D interfaces on unit deformation, but they cannot probe the atomic scale alone, so synthesis of computational results with experimental results is also discussed in Chapter 6. Chapter 7 concludes with a summary of key findings of this and proposes future work addressing new scientific issues raised by this work.