Effect of cryogenic temperature and change of strain path on grain refinement during rolling of Cu-30Zn brass

The effect of cryogenic temperature and change of strain path on grain refinement during the rolling of Cu-30Zn brass was determined. To this end, the material was unidirectionally rolled or cross-rolled to 90% thickness reduction at either ambient or liquid-nitrogen temperatures, and the resulting grain structures and crystallographic textures were determined via electron backscatter diffraction (EBSD) technique. In all cases, grain refinement was found to be governed primarily by twinning and shear banding. Lowering of the rolling temperature to the cryogenic range was found to provide only a minor effect. Cryogenic rolling was thus concluded to impart no practical benefit with regard to grain refinement or property improvement for this material. In contrast, a change of strain path via cross rolling was shown to enhance twinning and shear banding and thus to promote the formation of a relatively homogeneous ultrafine-grain microstructure.