Environment sensitive fracture of Al—Si—Mg alloy 6082

Abstract

Continuous and interrupted slow straining and cyclic loading have been employed to study the susceptibility of Al—Si—Mg alloys to environmen.t sensitive fracture over a wide potential range in tap water, sea water, and aqueous NaCl. Three possible regimes of reduced ductility have been identified; one associated with exfoliation attack at potentials anodic to the free corrosion potential, one at highly cathodic potentials attributable to hydrogen embrittlement at the bottom of corrosion pits, and an intermediate region in certain alloys, also attributable to hydrogen. The latter is dependent upon the breakdown of a protective film that tends to form on the alloys at these potentials. The dissimilar behaviour in different alloys is interpreted in terms of variations in magnesium, silicon, and iron content.