The effects of deformation parameters on the second phases and softening behavior of Al-Zn-Mg-Cu alloys

This study investigates the effects of deformation parameters on the second phase and softening behavior of Al-Zn-Mg-Cu alloy. The results are as follows: Firstly, the area fraction of the intermetallic phase fluctuates between 0.704 +/- 0.092% and 1.886 +/- 0.231% with varying deformation parameters. Secondly, in the temperature range of 270 degrees C to 430 degrees C, the area fraction of the eta[Mg(Zn, Al, Cu)(2)] phase first increases and then decreases with rising deformation temperature, and gradually increases with decreasing strain rate. The highest area fraction is 12.613 +/- 0.340% at 350 degrees C/0.001 s(-1), and the lowest is 0.366 +/- 0.068% at 470 degrees C/0.001 s(-1). Additionally, the coarsening and dissolution of the eta[Mg(Zn, Al, Cu)(2)] phase accelerate the dynamic recovery softening of the alloy. The sample at 350 degrees C/0.001 s(-1) shows a low-angle grain boundary (LAGBs) percentage of 97.83% and a minimum average dislocation density of 8.493 x 10(2) mu m(2). Furthermore, at 470 degrees C/0.001 s(-1), the Al7Cu2Fe phase has a weaker effect on stimulating nucleation and recrystallization, while the most significant promotion occurs at 430 degrees C/0.001 s(-1). In the range of 270 degrees C to 350 degrees C and 0.1 s(-1) to 0.5 s(-1), the Al7Cu2Fe phase mainly stimulates the formation of sub-grains. These findings offer valuable insights for refining the grain size of alloys by regulating the content of the second phase during hot deformation.