Development Process of Hetero-Nano Structure in a Cu-38 mass%Zn Alloy

The dependence of mechanical twinning on the crystallographic orientation at the early stage of rolling was investigated. For this purpose, a copper-zinc alloy plate having a sharp {001} texture on the rolling plane (normal direction // (001)) was prepared, and the twinning behaviors during rolling were studied in the grains with orientations of rolling direction (RD) parallel to (100), (210) and (110). The precise examination revealed that grains with RD // (110) orientation were most prone to twinning among the three crystallographic orientations. Effects of the development of heterogeneous-nano (HN) structure on the tensile properties were also systematically investigated. As the rolling reduction increased from 50% to 70%, the tensile strength increased significantly, and the elongation to failure also increased simultaneously. Considering the microstructural changes, the increase in the strength/ductility balance was attributed to the formation of the HN structure. Further rolling up to 90% resulted in a slight increase in strength anda significant decrease in ductility to about half of the value at 70%. It was suggested that the decrease in the volume fraction of twin domains in the HN structure, instead increase in the other texture components, during the rolling reduction from 70% to 90% complicatedly spoiled the strength/ductility balance.