Hot deformation behavior and microstructural evolution of as-quenched 7055 Al alloy fabricated by powder hot extrusion

Isothermal compression tests of powder hot-extruded 7055 Al alloy were carried out on a Gleeble-3180 thermosimulator at temperatures of 330-450 degrees C and strain rates of 0.001-1 s(-1). A processing map was established by superimposing the power dissipation map over the instability map at a true strain of 0.7. The results show that the instability domain tends to occur at high strain rates and low temperatures, and an optimum processing domain (360-420 degrees C, 0.001-0.013 s(-1)) is recommended. The softening mechanism of instability domain is manifested as dislocation accumulation and dynamic recovery (DRV), while that of the recommended domain is mainly coexistence of DRV and partial dynamic recrystallization (DRX). As the temperature increases and the strain rate decreases further, the dominant softening mechanism changes from dynamic recovery (DRV) to continuous dynamic recrystallization (CDRX). Strain-compensated Arrhenius model and artificial neuron network (ANN) model are constructed to predict the flow behavior of the alloy. Compared with the Strain-compensated Arrhenius model, the ANN model shows a better predictability with a lower average absolute relative error of 2.24%, a lower root mean square error of 1.21 MPa, and a higher correlation coefficient of 0.9987.