Stress corrosion cracking of alpha-beta brass in distilled water and sodium sulfate solutions

Specimens of a Cu-42 wt pct Zn alpha-beta alloy have been tested to failure in uniaxial tension at constant extension rates in a variety of environments. Testing in distilled H25O and 1 N Na2SO4 solutions over a range of potential-pH conditions results in large ductility losses and an interfacial + transgranular cleavage-like fracture mode. The electrochemical potentials of the specimens have been monitored and/or controlled during testing, and a shift to significantly more active open circuit potentials on straining is observed in environments which cause large ductility losses. The appearance of the transgranular beta fracture surfaces and the effects of potentiostatic polarization on the observed SCC behavior are similar to those seen for alpha phase Cu-Zn, which suggests that SCC of alpha and beta phase Cu-Zn are mechanistically similar. It is concluded that the observed behavior is most consistent with an SCC mechanism based upon the adsorption of a damaging species from the environment.