Microstructure and mechanical properties of 7A09 aluminium alloy after isothermal compression and solution treatment

In this paper, the effect of processing parameters on the microstructure was investigated during the isothermal compression of 7A09 aluminium alloy. The optimal deformation parameters for the hot compression of 7A09 aluminium alloy were determined to be 733 K and a strain rate of 0.01 s−1. The effect of solution temperature and solution time on the microstructure and mechanical properties of 7A09 aluminium alloy after isothermal compression was also investigated. A low deformation temperature was beneficial for preventing the grain coarsening, while a high deformation temperature contributed to the dissolution of the second phase particles and the occurrence of static recrystallisation during the solution treatment process. The second phase particles were more dissolved in the Al matrix as the solution time increased. The optimal solution treatment of 7A09 aluminium alloy was 723 K for 55 min, followed by rapid quenching in water and an ageing treatment at 413 K for 16 h. The tensile yield strength, ultimate strength, and elongation of 7A09 aluminium alloy after the optimal solution treatment were 580 MPa, 630 MPa, and 11.5%, respectively.

► Dynamic recovery is dominant softening mechanism at the deformation temperatures ranging from 673 K to 713 K. ► Dynamic recrystallisation occurs at 733 K and 0.01 s−1, which are the optimal deformation parameters in the work. ► The volume fraction of the recrystallised grains decreases with increasing strain rate. ► The second phase particles become more dissolved in the Al matrix with increasing solution time. ► The optimum heat treatment of 7A09 aluminium alloy is 723 K/55 min + 413 K/16 h.