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Potentiodynamic polarization and E corr versus t curves were obtained, together with electrochemical impedance spectroscopy (EIS) measurements, in order to understand the effects of alternating voltage (AV) passivation on the corrosion resistance of duplex stainless steel (DSS). SEM, EDS and XPS were employed to further investigate the influence of AV passivation on the properties of the passive film. The results of the electrochemical measurements showed that AV passivation significantly improved the corrosion resistance of DSS. SEM images indicated that the surface exhibited a unique morphology after AV passivation treatment, and XPS results suggested that AV passivation greatly increased the thickness of the passive film. Furthermore, significant chromium enrichment and a higher ratio of Fe 3? /Fe 2? were observed in the passive film after AV passivation. Mott-Schottky results confirmed that AV passivation had a strong influence on the semiconducting properties of the passive film.

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Ultrasonic additive manufacturing (UAM) is a novel solid-state freeform fabrication process that utilizes ultrasonic energy to merge similar/dissimilar metal tapes. Metallurgical bonding between the metal tapes can be achieved instantaneously once the sonotrode rotates through. Herein, five-layered Al-1100 ultrasonically consolidated samples are fabricated under various parameter combinations of ultrasonic amplitude and normal force settings. The microstructure and texture evolution of the built component among layers are characterized using electron backscattered diffraction (EBSD). The results reveal that among the upper layers, recrystallization only occurs at very local interface regions due to the local shear deformation, while the bulk region of each layer still remains the starting microstructure unaffected. However, after this cyclic accumulating process, dynamic recovery (DRV) and dynamic recrystallization (DRX) are observed to take place in the bottom of the built samples. The evolution of microstructures and textures of the bottom layer is a function of input energy, which well explains the effect of ultrasonic energy on the microstructure evolution at the metallurgical bonding regions.