A process for producing a black oxide coating on aluminum alloy was investigated in the present work. The blackening process is widely used in industrial applications, but it was not deeply studied for aluminum alloys. The aim of this work is to study the black coating obtained on AA6060 surfaces employing two different solutions, both containing potassium permanganate, copper nitrate and nitric acid. The first solution carried out the coloring treatment at 50 °C, whereas the second one was done at room temperature. Different immersion times were investigated. The morphology of the coating was investigated by means of optical and electron microscopy to evaluate the color of the layer and the presence of defects, porosities, and cracks. X-ray diffraction analysis was performed to evaluate the protective layer composition. The corrosion properties were studied with potentiodynamic polarization tests and electrochemical impedance spectroscopy tests. The results showed that the blackening process performed at room temperature, besides the clear advantages in term of costs and safety, obtained more uniform coatings with increased corrosion performance in comparison with the ones obtained at higher temperatures.
The microstructural evolution of a novel high‐silicon carbide‐free bainitic steel at different austempering temperatures is investigated. The microstructure is evaluated by means of optical and electron microscopy, X‐ray diffraction, microhardness, and nanohardness. Results show a variation in the amount of stabilized retained austenite changing the temperature of the isothermal treatment. In particular, it is observed an increase in the retained austenite volume fraction increasing the temperature up to 350 °C, while further increase leads to a reduction. Moreover, increasing the isothermal holding temperature from 250 °C, through 300, 350, and 370 °C, a progressive bainite coarsening and an increase in the amount of stabilized carbon‐enriched retained austenite are observed. Tensile tests reveal an excellent combination of mechanical properties: mechanical strength in the range 1276–1988 MPa and total elongation 0.18–0.44.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.