The microstructure of the high strength aluminum alloy, AA7475–T761, in the as-received condition was characterized by optical microscopy, scanning electron microscopy and transmission electron microscopy, and statistical analyses of grain size and micrometer precipitates distribution and density were performed. An anodic aluminum oxide (AAO) film was potentiostatically grown on the alloy in tartaric sulfuric acid (TSA). The anodizing behavior of the alloy and the mechanisms of localized corrosion initiation and propagation in bare (not anodized) and anodized conditions were discussed. The alloy corrosion behavior was investigated in sodium chloride solutions using electrochemical techniques (cyclic potentiodynamic polarization) and the morphology and extent of corrosion propagation was investigated through optical microscopy, optical profilometry and scanning electron microscopy analyses. It was observed that the two alloy surface conditions (bare and anodized) play different roles in the propagation of the localized corrosion process. The bare alloy presented lower localized corrosion potentials and the propagation of the localized corrosion was shallower, but more heavily distributed, than in the anodized condition. However, the alloy in the anodized condition presented lower repassivation potentials due to the deeper pits formed. In addition, the variability of pitting potentials for the anodized condition was high, due to the heterogenous structure of the AAO film formed, and dependent on the time and drying storage conditions previous to electrochemical characterizations. The electrochemical results were correlated with the microstructural characteristics of the oxide surface film of the alloy in both conditions, bare (not anodized) and anodized.
Biodegradable metallic scaffolds are interesting biomaterials for applications in temporary implants for bone regeneration because of their good mechanical properties. In addition, the need for a second surgery to remove the implant is reduced if biodegradable metals are used. Fe has adequate mechanical properties for scaffolds manufacture and suitable biocompatibility. However, Fe shows slow biodegradation rates for the application and, therefore, different approaches have been developed such as the development of alloys or by reducing the thickness of the Fe strut in the scaffold. FeMn alloys are considered ideal materials, as they are not ferromagnetic. In addition, additive manufacturing technologies (3D printing) are considered appropriate to manufacture these scaffolds due to the ability to obtain complicated geometries and customized parts for a specific bone injury site. Electrodeposition is also an interesting technique because it allows the deposition of thinner strut walls of Fe (or alloys) with high purity, in addition to providing a good surface finishing. The aim of the first part of this work is to electrodeposit thin films of FeMn alloys and to evaluate its microstructure and mechanical properties. The thin films were electrodeposited potentiostatically from sulfate electrolytes with different concentrations of FeSO4 and MnSO4. The effect of deaeration, substrate material and electrodeposition potential were evaluated. The microstructure of the electrodeposited films was characterized by SEM/EDX and XRD. The surface finishing was evaluated by AFM and the mechanical properties by microhardness measurements.
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