Bulk Cu-Zn alloy was multi-directionally forged at 77 and 300K to a cumulative strain of 6.0. With increasing strain, the initial grains sub-divided gradually to give ultra-fine grains. Mechanical twins enhanced the grain fragmentation. The twins thus formed were further sub-divided by other twin variants. The grain size obtained at a cumulative strain of 6.0 was about 17nm at 77K and 26nm at 300K.

Enhanced Grain Refinement by Mechanical Twinning in a Bulk Cu-30 wt%Zn during Multi-Directional Forging. H.Miura, Y.Nakao, T.Sakai: Materials Transactions, 2007, 48[9], 2539-41