Mechanism of Stress-Corrosion Cracking in Brass

A stress-strain curve has been determined to investigate the mechanism of stress-corrosion cracking in the brass-ammonia system in reference to the role of the surface film. The corrosion behavior of surface slip lines produced in a intergranular cracking environment and the fracture surface have also been examined using optical and electron microscopes.In the intergranular cracking environment both stress and strain required to cause failure showed larger values than those in the transgranular cracking environment. This was explained in terms of a concept that a tarnish layer is formed on the specimen surface in the intergranular cracking environment and the layer arrests the movement of surface dislocations. From the observations of the slip lines and fracture surfaces, it was concluded that the mechanism of stress-corrosion cracking varies depending on the strain rate or stress level in a constant load test.