Microstructures and Mechanical Properties of Cu-38 mass%Zn Alloy Fabricated by Different Rolling Pass Schedules

The heterogeneous-nano (HN) structure consisting of twin domains, shear bands, and lamellar grains developed by heavy cold rolling of FCC metals with low stacking fault energy is known to provide extremely high strength. In the present study, the effects of the rolling pass schedule on the development of HN structure and the mechanical properties in a Cu-38 mass%Zn alloy were investigated. Rolling was conducted on two different pass schedules; one was conventional unidirectional rolling (1-DR) up to 90% reduction in thickness, and the other was the two-directional rolling (2-DR), in which the specimen was unidirectionally rolled to 25% reduction, then rotated 90 degrees around the rolling direction, and subsequently, unidirectionally rolled up to the total reduction of 90%. At a total reduction of 50%, the number of grains with deformation twins in the 2-DR specimen was higher than that in the 1-DR specimen. Further cold rolling up to 90% produced the HN structure in both specimens. The size of twin domains in the 2-DR specimen was finer and their volume fraction was larger than those in the 1-DR specimen. Also, the 2-DR specimen exhibited a better strength-elongation balance than the 1-DR specimen. It can be concluded that the finer size and larger volume fraction of the twin domains effectively improved the strength-elongation balance in the 2-DR specimen.