Stress corrosion cracking of [110] and [100] tilt boundaries of α-Cu-Al alloy

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Abstract
Intergranular stress corrosion cracking (SCC) of Cu–9 at.% Al alloy bicrystals with symmetrical [110] and [100] tilt boundaries has been investigated under constant applied stresses in an ammoniacal solution at 303 ± 2 K. The susceptibility, defined by the inverse of time spent for initiation and propagation of the brittle crack along the boundary, was found to be strongly dependent upon the misorientation. Susceptibility minima were found at misorientations where interfacial energy cusps have been often observed in copper and aluminium in the literature. The grain-boundary energy is considered to be one of the crucial factors which determine the susceptibility. It is suggested that the susceptibiliy is affected by the dislocation behaviour at a grain boundary. A stress field generated as a result of interaction between lattice dislocations and a grain boundary may reduce the resistance to intergranular SCC. The susceptibility rapidly decreases, most probably owing to the increase in dislocations passing through a grain boundary on decreasing the misorientation from approximately 20 to 15°.