Effects of atmosphere in filament formation on a superplastically deformed aluminum–magnesium alloy

Filaments with diameters of the order of 1 μm were observed on fracture surfaces of a fine-grained aluminum–magnesium alloy following superplastic deformation in air. No filaments were observed on fracture surfaces of the same material after superplastic deformation at identical temperature and strain rate in vacuum. Filaments contain oxygen and more magnesium than does the as-received specimen surface. These data support the theory that filaments are formed on fracture surfaces by growth of magnesium-rich oxide.