Effects of four different pre-treatments including annealing

deformation

dual aging

RRA on Al-Zn-Mg-Cu alloy in ECAP have been described.The results show that the annealed alloy at room temperature can only be pressed two passes

while the other alloys are seriously cracked after pressing first pass in ECAP.In addition

the annealed alloy can be pressed many passes with annealing at 523 K

in which the grain size is obviously refined and gradually evolved into equaixed grain with increasing in ECAP passes

however

the refinement of grain size is greatly decreased after eight passes

and the equivalent true strain reaches up to 6.2 after 10 passes with the equaixed grain of about 0.8μm in size.The hardness of annealed alloy is increased with increasing passes

showing a quantitative relationship.