Abstract
Anodized specimens of aluminum and tantalum were deformed in laboratory air; strain to failure and the failure characteristics of the oxide film were evaluated optically. Barrier‐type anodic aluminum oxide films of thickness greater than ∼400Å failed at ∼0.925% strain normal to the tensile axis and apparently suppressed substrate slip emergence. Thinner anodic films on aluminum failed along substrate slip traces at ∼1.12% strain. These films did not suppress slip emergence, but were apparently stronger. The presence of a porous oxide superimposed on thin barrier‐type films caused them to fail in the thick film mode; this was the only effect of a porous layer. Anodic films on mechanically polished tantalum failed at ∼0.28% strain, independent of thickness, but showed a failure mode dependence on thickness analogous to that of aluminum. Films on chemically polished tantalum substrates always failed in simple tension, but showed a thickness dependence, failing at ∼0.14% strain for thicknesses greater than ∼680Å, and ∼0.20% strain for thicknesses less than that value. Failure of these films was accompanied by separation of the films from the substrate.