Inhomogeneity of anodic oxide films of Al and Al alloys characterized by scanning electron microscopy observation and analysis of frequency response behavior

When nickel-plated steel is heated to temperatures required for hot rolling, the familiar “alloy layer” zone is observed in the microstructure. Preliminary observations in the Castaing electron probe microanalyzer showed that this zone is merely a region of solid solution in which composition varies widely. No obvious meaning can be attached to the composition limits of the iron-rich and nickel-rich sides of this zone. A systematic investigation has been carried out to study the interdiffusion of the two metals.