Slip Behavior at the Early Stage of Plastic Deformation in a Polycrystalline Cu-30 mass%Zn Alloy

Slip bands formed at the low strain region ranging from about 0.005 to 2% in a polycrystalline Cu-30 mass% Zn alloy were investigated by optical microscopy and crystallographic orientation analysis using an SEM-ECP method. Many grains exhibited slip bands caused by the primary slip system at about 0.005% strain. Some grains in which the secondary slip system had been activated were observed at this stage of plastic deformation. Most of these grains produced slip bands due to the primary slip system with further plastic deformation. A model of Hashimoto and Margolin based on the elastic incompatibility at a grain boundary could explain the secondary slip system becoming active in only about 20% of the grains in which this slip system had been activated initially. In about 60% of such grains, when the secondary slip system produced more similar shape change to that of the surrounding grains than the primary slip system did, the secondary slip system was understood to become preferentially active, taking account of the two-dimensional surface shape change after small plastic deformation.