Abstract
Results are described for stress-corrosion experiments carried out on oriented single crystals of copper-gold and copper-zinc (α-brass) using constant load and slow strain-rate loading modes under various chemical conditions in which passive oxides or dealloying in the absence of films are present at the surface. Evidence is presented to support the role of localized dissolution at slip traces in crack-initiation at a free surface, as well as in the re-nucleation of arrested cracks. The orientations of fracture surfaces are predominantly {110} independent of the tensile axis orientation, with the occasional appearance of {111} fracture planes in α-brass. Common fractographic features are seen in all systems studied, including the presence of crack-arrest markings. Dissolution of α-brass in cupric-ammonia solutions produces faceted pits with characteristic morphologies reflecting the symmetry of the exposed surfaces; whereas, dissolution in a cuprous-ammonia solution in equilibrium with copper produces minimal attack and no pitting. None of these morphologies for specimens corroded in the non-equilibrium or equilibrium solutions, with or without static or dynamic loading were observed to be associated with the characteristic surface morphology of T-SCC surfaces. These results are discussed in terms of the applicability of the Corrosion-Assisted Cleavage (CAC) model.
