Abstract

The hot deformation behavior of 7050 aluminum alloy was investigated by isothermal compression tests over a temperature range of 250 °C to 450 °C and a strain-rate range of 0.001 s−1 to 1 s−1. The flow stress was strongly dependent on both temperature and strain rate. At a strain rate of 0.1 s−1, increasing the temperature from 250 °C to 450 °C reduced the peak stress by 72.7%. At 450 °C, decreasing the strain rate from 1 s−1 to 0.001 s−1 reduced the peak stress from 66.7 MPa to 14.6 MPa, corresponding to a decrease of 78.1%. Based on the peak stress, an Arrhenius-type constitutive equation was established, with a deformation activation energy of 179.35 kJ mol−1. The predicted peak stresses agree well with the experimental values, giving a correlation coefficient (R2) of 0.98. The processing map indicates that the optimal hot working domain is located at 400–450 °C and 0.001–0.05 s−1. Scanning electron microscopy (SEM) observations showed that increasing temperature promoted the reduction in second-phase particles, with their area fraction decreasing from 5.3% at 250 °C to 1.2% at 450 °C under 0.001 s−1. In comparison, strain rate had a smaller effect on the particle area fraction at 450 °C. Electron backscatter diffraction (EBSD) analysis revealed that high temperature and low strain rate enhanced dynamic recovery and grain-boundary misorientation evolution. The fraction of low-angle grain boundaries (LAGBs) decreased from 71.5% to 38.8% as the temperature increased from 250 °C to 450 °C under 0.001 s−1, and decreased from 48.2% to 38.8% when the strain rate decreased from 1 s−1 to 0.001 s−1 at 450 °C.

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