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While trade relations between French colonists and indigenous peoples in New Orleans are well documented, there have been few in depth studies utilizing archaeological sites in the city to illuminate the ways in which such relations shaped the day to day lives of the peoples involved. This work has attempted to elucidate trade practices between these groups by utilizing archaeological data uncovered at 810 Royal Street during excavations from 2015 through 2018. A collection of hand-built ceramics typically associated with indigenous peoples found in French colonial contexts on the site may help explicate the nature of trade occurring within the city and the ways in which this trade was reflective of larger patterns of urban colonial adaptation and creolization. This work seeks to illuminate the motivations behind such trade and the ways in which economic motives and individual self-interests drove colonists to undermine the original French designs for the city.

The Al-Zn-Mg-Cu (7XXX series) alloys are amongst the strongest aluminum available. However, they are considered unweldable with conventional fusion techniques due to the negative effects that arise with conventional welding, including hydrogen porosity, hot cracking, and stress corrosion cracking. For this reason, friction stir welding has emerged as the preferred technique to weld 7XXX series alloys. Aluminum 7449 is one of the highest strength 7XXX series aluminum alloy. This is due to its higher zinc content, which leads to a higher volume fraction of eta' precipitates. It is typically used in a slight overaged condition since it exhibits better corrosion resistance. In this work, the welds of friction stir welded aluminum 7449 were studied extensively. Specific focus was placed in the heat affected zone (HAZ) and nugget. Thermocouples were used in the heat affected zone for three different depths to obtain thermal profiles as well as cooling/heating profiles. Vicker microhardness testing, transmission electron microscope (TEM), and differential scanning calorimeter (DSC) were used to characterize the welds. Two different tempers of the alloy were used, a low overaged temper and a high overaged temper. A thorough comparison of the two different tempers was done. It was found that highly overaged aluminum 7449 tempers show better properties for friction stir welding. A heat gradient along with a high conducting plate (Cu) used at the bottom of the run, resulted in welds with two separate microstructures in the nugget. Due to the microstructure at the bottom of the nugget, higher strength than the base metal is observed. Furthermore, the effects of natural aging and artificial aging were studied to understand re-precipitation. Large improvements in strength are observed after natural aging throughout the welds, including improvements in the HAZ.

The objective of this study was to quantitatively study localized corrosion, especially exfoliation corrosion (EFC) of high strength aluminum alloys and to investigate the mechanism of exfoliation corrosion with a focus on the effects of alloy temper, microstructure, relative humidity (RH) and mechanical stress. A new technique, Exfoliation of Slices in Humidity (ESH), was developed for the determination of exfoliation corrosion (EFC) susceptibility and quantification of EFC kinetics. This technique involves in exposing properly oriented and unconstrained samples to high humidity following an electrochemical pretreatment. The EFC kinetics was determined by measuring the width of the central unattacked region of the samples. The ESH results show the capability of the ESH test to discriminate between plates of varying susceptibility and to determine EFC rates quantitatively. Optical microscopy and analytical TEM were used to investigate the effects of microstructure and local chemistry at grain boundary on EFC susceptibility. Alloys with more elongated grain shape are more susceptible to EFC and a high Zn content in grain boundary precipitate free zone relates to a high susceptibility. The effects of RH, temper and applied stress on EFC kinetics of AA7178 were investigated by ESH tests. The critical RH for EFC propagation in AA7178 was found to be about 56% and the EFC kinetics increased with RH. ESH tests provide a quantitative description of the temper effect on EFC kinetics. The effects of applied compressive and tensile stresses on EFC kinetics were studied using a four-point bending jig. Compression accelerated EFC significantly and tension reduced kinetics. An equation describing the effects of RH, stress and time on EFC kinetics was developed based on the ESH results using Eyring model. In situ X-ray radiography was used to characterize intergranular and exfoliation corrosion in high strength Al alloys. The samples were either exposed to sodium chloride solution (NaCl) at a controlled potential or to high humidity after an electrochemical pretreatment in NaCl solution. In situ X-ray radiography of intergranular corrosion attack provides a wide range of IGC kinetics including the fastest growing sites. This method is a good approach for visualizing the EFC process.

High strength 7xxx aluminum alloys used widely in aircraft structure are very susceptible to intergranular corrosion (IGC). From a practical point of view, it is important to understand IGC in these alloys. Measuring the kinetics of IGC is not only a way to evaluate corrosion susceptibility, but also very useful for a predictive model for corrosion. Several AA7075 and AA7178 plates were used in this work. The foil penetration technique was used to measure the localized corrosion kinetics of the alloys in a NaCl solution and a new approach was developed to quantify the growth rates of sharp IGC fissures in a humid environment. Electrochemical properties of the alloys were studied by measuring the polarization curves. Electron microscopy and analytical techniques were used to observe the corrosion morphology and to understand the IGC mechanism. Localized corrosion kinetics were measured on several alloys with different grain aspect ratio to understand the influence of grain structure. Anisotropic corrosion kinetics were found on alloys with grain aspect ratio greater than 1. Metallographic cross-sections confirmed that the localized corrosion kinetics strongly depend on the IGC growth path, which was affected by the microstructural anisotropy of the material. It was also found that IGC morphology of AA7xxx was selective grain attack (SGA) in a NaCl solution and was sharp fissure in a humid environment. A statistical model for corrosion in AA7xxx was developed based on the grain structure of the material and the foil penetration data. Scenarios for SGA mechanism were proposed according to the statistical method and simulations. The sharp IGC fissure growth kinetics were found to be independent of the humidity from 96% to 58% RH due to little connection of the local sites to the external environment. The sharp IGC fissures were found to be filled with corrosion products that seem to drive fissure growth by an SCC mechanism.