The bulky ultra-fine 2A12 aluminum alloy with grain size about 200 nm and high angular boundary can be prepared by 8-turns pressing with ECAP die with the inner angle 90 and outer angle 30 at ambient temperature

and the microstructure and its evolution of the 2A12 aluminum alloy during pressing were observed by Hitachi S-800 TEM. The results show that grain size is significantly refined due to the sharply increases of dislocation density in grain resulting in dislocation tangle after one-turn pressing. Needle-like secondary phase Al2Cu is transformed into particle

dispersing in a-Al matrix

and Al2 CuMg particle is pressed into grain boundary due to the refinement of the grain size with shearing

where these compound particles are not changed in the following pressing process. The 2A12 aluminum alloy with ultra-fine structure can be prepared due to the dislocation gradually moving from grain towards grain boundary

and forming cell structure on grain boundary

finally gradually becoming clear small angular boundary or large angular boundary by continuously pressing.