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Near-surface deformed layers, which are characterized by nano-sized fine grains, are generated in aluminum alloys by hot and cold rolling. During the rolling processes, the alloy surface and near-surface regions experience a high level of shear deformation that results in significant microstructure refinement, leading to formation of near-surface deformed layers with microstructures different from that of the underlying bulk alloy. Two types of near-surface deformed layers are observed. Type A is characterized by fine grains with grain boundaries decorated by oxide particles; type B is characterized also by fine grains but with the grain boundaries free of oxide particles. The high levels of shear deformation result in dynamic recrystallization. Together with mechanical alloying, this is responsible for the formation of the near-surface deformed layer. Furthermore, the structure in the near-surface deformed layer can survive the typical annealing process particularly if the grain boundaries are pinned by oxide particles.

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The electrochemical behavior of a range of Al‐Ga alloys was determined in 4M normalNaOH and 2M normalNaCl both under normal polarization conditions and in a small battery designed for viewing reacted anodes in a scanning electron microscope. The observed behavior was compared with that of gallium and Ga‐0.1% Al. It was found that the electrochemistry of Al‐Ga was controlled by that of gallium in as much as Al‐Ga alloys with low levels of gallium could only display active behavior in alkali if initially polarized below the normalGa/GaO33− reduction voltage. The activation phenomenon took place at localized surface sites associated with gallium agglomerates, a likely mechanism being rapid diffusion of aluminum through the gallium particles which seemed to prevent the normal, passive behavior of aluminum. The speed of activation after current switch‐on varied inversely with alloy gallium concentration and depended on a critical surface concentration of gallium being achieved. Back‐diffusion of gallium away from the surface strongly influenced the activating capabilities of alloys with lower levels of gallium. Cooling of activated Al‐Ga alloys resulted in deactivation caused by surface gallium solidification and passivation.