Abstract
In order to study the corrosion behavior of the α+β alloy, the immersion test and the measurement of the natural potential of a 60/40 brass sheet which was cold-rolled up to 90% total reduction under the condition of 5% reduction per pass, have been carried out in a 3 mass%NaCl aqueous solution, and the residual stress and the rolling texture have been investigated by means of X-ray diffraction. The corrosion rate curve obtained showed a maximum value at 50% reduction, subsequently decreased at 80% total reduction, and then increased slightly at 90% total reduction. The relation between the immersion time and the natural potential resembled the relation between corrosion rate and total reduction as the tendency of the curve was inverted, and the same is true for the relation between the residual stress and total reduction. As the dominant factor of corrosion, the dependence of crystal orientation or the priority solution of the β phase can hardly be considered, and the effect of residual stress is deduced to play the main role. From the microstructure observations of the rolling surface and the longitudinal section, the β phase was stable up to approximately 40% total reduction and the rolling deformation was carried out mainly in the a phase, but at heavy deformations a singular plastic deformation with a activity of shear bands occurred in the β phase, thus contributing to plastic deformation greatly. Consequently, it is deduced that due to such a vigorous activity the inner stresses which were accumulated at a grain or phase boundary are released and there by the residual stress decreases.
