Copper powder was sprayed by the cold-gas dynamic method. In-flight particle velocities were measured with a laser-two-focus system as a function of process parameters such as gas temperature, gas pressure, and powder feed rate. Particle velocities were uniform in a relatively large volume within the plume and agreed with theoretical predictions. The presence of the substrate was found to have no significant effect on particle velocities. Cold-spray deposition efficiencies were measured on aluminum substrates as a function of particle velocity and incident angle of the plume. Deposition efficiencies of up to 95% were achieved. The critical velocity for deposition was determined to be about 640 meters per second.

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A study has been made of how impurities (Na and K) and trace additions of indium, magnesium, and silicon affect the microstructure and related mechanical properties of an Al-Cu-Li alloy. Transmission electron microscopy (TEM) was used to determine the size and distribution of particles in four alloys. Indium and magnesium are both seen to stimulate T 1 precipitation. Indium also modifies " morphology, and magnesium greatly increases the number density of " precipitates. Strain localization was observed in underaged Al-Cu-Li-In tensile samples, consistent with observed changes in precipitate structure. No superposition of the effects of indium and magnesium was seen. Highresolution analytical microscopy was used to inspect precipitates for segregation of trace elements during early stages of aging, but no segregation was found within the detection limits of the system. Variations in heat treatment were made in order to study nucleation kinetics and trace element interactions with vacancies. Indium, with a binding energy less than that of lithium, was not seen to interact with quenched-in vacancies, while magnesium, with a binding energy greater than that of lithium, had a strong interaction. Yield anisotropies and fracture toughnesses were measured. Removal of trace impurities of sodium and potassium correlated with improved fracture properties. Magnesium was observed to increase anisotropy, especially in the T8 temper. A model was used to explain the anisotropy data in terms of texture and precipitate distribution.

A photoelectrochemical anodization technique has been used to fabricate n-Si/insulator/metal (MIS) diodes with improved electrical properties. MIS structures fabricated with Au have provided the first experimental observation of a solid-state n-Si surface barrier device whose open circuit voltage Voc is controlled by minority-carrier bulk diffusion/recombination processes. For these diodes, variation of the minority-carrier diffusion length and majority-carrier dopant density produced changes in Voc that were in accord with bulk diffusion/recombination theory. Additionally, the variation in Voc in response to changes in the work function of the metal overlayer indicated that these MIS devices were not subject to the Fermi level pinning restrictions observed for n-Si Schottky structures. X-ray photoelectron spectroscopic characterization of the anodically grown insulator indicated 8.2±0.9 Å of a strained SiO2 layer as the interfacial insulator resulting from the photoanodization process.

Direct fabrication of metal near-net shapes from a computer model typically involves melting and solidification, which can cause high residual stresses, undesirable phases, poor microstructures, rough surface finishes, warpage, and other problems. This paper describes a new technology, still under development, that might be used to directly fabricate solid, near-fulldensity, free-form shapes of many metals, and even some composite materials, at or near room temperature without melting and solidification. In this process, tentatively called Cold Spray Direct Fabrication (CSDF), powder particles in a supersonic jet of compressed gas impact a solid surface with sufficient energy to cause plastic deformation and consolidation with the underlying material by a process thought to be analogous to explosive welding. Material deposition by cold spray methods has already been successfully demonstrated by several investigators. This paper presents results of an experimental study to investigate the effects of selected process variables on cold spray particle velocities. In addition, a key technical barrier to the CSDF concept is focusing the spray stream down to dimensions that would permit a useful level of part detail, while still providing practical build rates. This paper presents results of initial research to develop an aerodynamic lens that may provide the required particle stream focusing.

This is the second paper of a two part series based on an integrated study carried out at the State University of New York at Stony Brook and Sandia National Laboratories. The goal of the study is the fundamental understanding of the plasma-particle interaction, droplet/substrate interaction, deposit formation dynamics and microstructure development as well as the deposit properties. The outcome is science-based relationships, which can be used to link processing to performance. Molybdenum splats and coatings produced at three plasma conditions and three substrate temperatures were characterized. It was found that there is a strong mechanical /thermal interaction between droplet and substrate, which builds up the coating/substrate adhesion. Hardness, thermal conductivity increase, oxygen content and porosity decreases with increase of particle velocity. Increasing deposition temperature resulted in dramatic improvement in coating thermal conductivity and hardness as well as increase in coating oxygen content. Indentation reveals improved fracture resistance for the coatings prepared at higher deposition temperature. Residual stress was significantly affected by deposition temperature, although not to a great extent by particle conditions within the investigated parameter range. Coatings prepared at high deposition temperature with high-energy particles suffered considerably less damage in a wear test. The mechanism behind these changes is discussed within the context relational maps which is under development.