The correlation between flow behavior and microstructural evolution of 7050 aluminum alloy

The flow behavior and the microstructural evolution of 7050 aluminum alloy are investigated at the deformation temperatures ranging from 593 K to 743 K, strain rates ranging from 0.01 s−1 to 20.0 s−1, and height reductions ranging from 30% to 70%. The processing maps at the strains of 0.4 and 0.7 are developed on the basis of dynamic materials model (DMM). The results show that the deformation temperature and the strain rate have obvious effect on the flow stress and the microstructure of 7050 aluminum alloy. The steady flow stress–strain curves at the strain rates below 10.0 s−1 and the deformation temperatures above 703 K show continuous dynamic recrystallization character. However, a continuous flow softening behavior at high strain rates (≥10.0 s−1) implies the occurrence of flow instability or cracking in isothermal compression. The samples isothermally compressed at 10.0 s−1 or 20.0 s−1 and 723 K exhibit cracking. The processing maps at a strain of 0.7 exhibit two regions with high efficiency of power dissipation in isothermal compression of 7050 aluminum alloy. One is in the deformation temperature range from 614 K to 673 K and the strain rates below 0.022 s−1, and another is in the deformation temperature range from 718 K to 743 K and the strain rates below 0.018 s−1. On the basis of the processing maps and microstructural examination, the optimal processing parameter of 7050 aluminum alloy at a strain of 0.7 corresponds to a deformation temperature of 723 K and strain rate of 0.01 s−1.

► The samples deformed at 10.0 s−1 or 20.0 s−1 and 723 K exhibit cracking.
► The steady flow curves above 703 K and below 10.0 s−1 show continuous dynamic recrystallization character.
► Dynamic recovery is main softening mechanism below 703 K in all strain rate range or above 703 K and above 10.0 s−1.
► The optimal processing parameter of 7050 aluminum alloy at a strain of 0.7 is 723 K and 0.01 s−1.