CCDC Army Research Laboratory Aberdeen Proving Ground United States
The objective of this work is to explore the feasibility of a novel severe surface plastic deformation process to simultaneously improve the corrosion resistance of the substrate while imparting desired surface chemistry and morphology. This limited scope project has two aims 1 quantify the ways in which a gradient microstructure achieved through this method can enhance the corrosion resistance of a treated aluminum alloy substrate and 2 extend and develop this surface treatment to engender a surface alumina layer in single-step method without hazardous chemical processes. This limited scope program has shown the feasibility of the Surface Mechanical Alloying for Specialized Heterogeneity SMASH treatment to improve the corrosion response of aluminum alloy AA5083. The mechanism for this improvement reduction of magnesium content into the depth of the substrate as a result of plastic deformation is not one that has been observed before in other methods of severe plastic deformation applied to AA5083 and opens up new methods for improving sensitization behavior of aluminum magnesium alloys. The SMASH process was successful in producing an alumina layer 20-100 m thick on aluminum alloy substrates through a mechanical mixing approach that uses only powder as input and discard e.g., no acid baths as hazardous waste. However, the coatings have a range of particle distribution and are morphologically very different from traditional anodized coatings. Significant further testing is necessary to determine how this would affect adhesion and wear.