The Relationship Between Dealloying and Transgranular Stress‐Corrosion Cracking of Cu‐Zn and Cu‐Al Alloys

Single crystals of various α‐phase Cu‐Zn and Cu‐Al alloys have been tested for dealloying and stress‐corrosion cracking (SCC) in cuprous ammonia solutions. All tests were done at the equilibrium potential of a copper electrode. The dealloying tests were done by scratching coated specimens and measuring the consequent anodic current transients, and the SCC tests used a constant extension rate. The rate of dealloying increased almost discontinuously between 17 and 20 atom percent (a/o) Zn and between 11 and 16 a/o Al. These "parting limits" corresponded identically to the onset of transgranular SCC in both systems. The results support a percolation model of dealloying and a film‐induced cleavage model for stress‐corrosion cracking.