High energy neutron and proton radiation can induce serious damage in structural metals, including void swelling and embrittlement. Hence the design of advanced metallic materials with significantly enhanced radiation tolerance is critical for the application of advanced nuclear energy systems. The goals of this dissertation are to examine the fundamental physical mechanisms that determine the responses of certain metallic multilayers, with ultra-high density interface structures, to plastic deformation and high fluence He ion irradiation conditions. This dissertation focuses on the investigation of mechanical and radiation responses of Al/Nb and Fe/W multilayers. Radiation induced microstructural evolution in Cu and Cu/Mo multilayer films are briefly investigated for comparisons. Al/Nb multilayer films were synthesized by magnetron sputtering at room temperature. The interface is of Kurdjumov-Sachs orientation relationship. In situ nanoindentation inside a transmission electron microscope (TEM) reveal that interfaces act as strong barriers for dislocation transmission and dislocations climb along the Al/Nb interfaces at a much higher velocity than in bulk. The evolution of microstructure and mechanical properties of Al/Nb multilayers has been investigated after helium ion irradiations: 100 keV He+ ions with a dose of 6x10^16/cm2. When layer thickness, h, is greater than 25 nm, hardness barely changes, whereas radiation hardening is more significant at smaller h. This study shows that miscible fcc/bcc interface with large positive heat of mixing is not stable during ion irradiation. In parallel we investigate sputtered Fe/W multilayers. Film hardness increases with decreasing h, and approaches a maximum of 12.5 GPa when h = 1 nm. After radiation, radiation hardening is observed in specimens when h>/= 5 nm, however, hardness barely changes in irradiated Fe/W 1 nm specimens due to intermixing. In comparison, Cu/Mo 5 nm multilayers with immiscible interface has also been investigated after helium ion irradiations. Interfaces exhibit significantly higher helium solubility than bulk. He/vacancy ratio affects the formation and distribution of He bubbles. The greater diameter of He bubbles in Cu than Mo originates from the ease of bubble growth in Cu via punching of interstitial loops. Finally, helium bubble migration and growth mechanisms were investigated in irradiated Cu (100) single crystal films via in situ heating inside a TEM. The activation energy for bubble growth is ~ 0.02 eV at low temperature. At higher temperatures, the activation energy for bubble coalescence is ~ 0.22 eV inside crystal, and 0.34 eV close to surface. The migration mechanisms of helium bubbles involve continuous as well as Brownian movement.

The development of multilayer structures has been driven by a wide range of commercial applications requiring enhanced material behaviors. Innovations in physical vapor deposition technologies, in particular magnetron sputtering, have enabled the synthesis of metallic-based structures with nanoscaled layer dimensions as small as one-to-two monolayers. Parameters used in the deposition process are paramount to the Formation of these small layer dimensions and the stability of the structure. Therefore, optimization of the desired material properties must be related to assessment of the actual microstructure. Characterization techniques as x-ray diffraction and high resolution microscopy are useful to reveal the interface and layer structure-whether ordered or disordered crystalline, amorphous, compositionally abrupt or graded, and/or lattice strained Techniques for the synthesis of metallic multilayers with subnanometric layers will be reviewed with applications based on enhancing material behaviors as reflectivity and magnetic anisotropy but with emphasis on experimental studies of mechanical properties.

The MRS Symposium Proceeding series is an internationally recognised reference suitable for researchers and practitioners.

This book contains a series of lectures given in a Summer School held in Aussois (France) in September 1989. It offers a global perspective on the current state-of-the-art in the rapidly emerging field of metallic multilayered structures.

In the fall of 1998, Prof. Sergey Firstov invited me to the Frantcevych Institute for Problems of Materials Science (IPMS) in Kyiv, Ukraine to discuss possible collaborations in the area of advanced metals research. During this visit, a strong mutual interest was evident in a broad range of structural metals technologies, and a quick friendship was established. Countless subsequent emails and a reciprocal visit to the U. S Air Force Research Laboratory by Prof. Firstov and a team of scientists from IPMS ensued to discuss and detail a broad collaboration in the area of structural metals. Two years after the initial visit, a major investment by the U. S. Air Force Office of Scientific Research (AFOSR) was established to pursue the technologies defined by these interactions. The annual reviews of the AFOSR Ukrainian Metals Initiative were held in late May, a most beautiful time in Kyiv when the lilacs are in bright display and the air is scented with the smell of falling blossoms from the chestnut trees that line the major streets and many parks. The sunny days and mild evenings provide a welcome break from winter, and on weekend evenings festive crowds spill onto the Khreshchatyk, Kyiv’s downtown boulevard, to listen to street musicians, watch jugglers and comedians, or simply to celebrate with friends. The annual reviews featured long days of intensive discussion of technical progress, followed in the evenings by the warm hospitality of the Ukrainian hosts.

Abstract: Modeling the defect structure and mechanical properties of metallic multilayer thin films requires estimates of dislocation parameters such as interfacial line energy, interfacial barrier strength, and resistance to confined layer slip (CLS). A method is presented to estimate these parameters using experimental measurements of hardness and internal stress vs. individual layer thickness, h. Cu/Ni multilayers of varying bilayer thickness (20 nm

Structural and Morphological Evolution in Metal-Organic Films and Multilayers presents major results of the authors' work carried out on Langmuir monolayers and Langmuir-Blodgett multilayers. The authors address two important questions:Are metal-organic monolayer systems more like solids or more like liquids?Does a two-dimensional system have diffe

Constant-stress molecular dynamics simulations are used to study the mechanical properties of equal concentration Cu-Ni (111) metallic multilayers of repeat lengths 0.4--0.5 nm. Uniaxial stress is applied along the close-packed and perpendicular to the close-packed directions within the (111) plane. The observed elastic moduli do not display a supermodulus effect as observed in experimental bulge tests for the biaxial modulus. However, both the average interlayer spacing and the out-of-plane Poisson ratio display anomalous effects for multilayer repeat lengths below about two nanometers.

Bulk metallic glasses are a new emerging field of materials with many desirable and unique properties. These amorphous materials have many diverse applications from structural applications to biomedical implants. This book provides a complete overview of bulk metallic glasses. It covers the principles of alloy design, glass formation, processing, atomistic modeling, computer simulations, mechanical properties and microstructures.