Film-Induced Brittle Intergranular Cracking of Silver-Gold Alloys

Dealloying of a binary noble alloy produces a porous layer rich in the more noble element. Application of a tensile load initiates a brittle intergranular (IG) crack in the dealloyed layer that advances into the unattacked material. This study showed that the crack penetration depth (C_d) is proportional to the thickness of the dealloyed layer (t). For a given value of t, the grain-boundary crack penetration distance was shown to decrease as the dealloying potential increased. The dependence of C_d on t and the dealloying potential as opposed to the applied potential at the time of fracture, supported the film-induced cleavage model.