Effect of Plastic Anisotropy on the Kinetics of Static Softening in AA2024–T3 Aluminum Alloy

The influence of plastic anisotropy on the static softening kinetics after cold forming in the AA2024–T3 aluminum alloy sheet was investigated. The uniaxial tensile tests were carried out at room temperature in three directions 0°, 45° and 90° in relation to the rolling direction, at 8% strain level. The samples were then annealed at 350 °C for various holding times. The softening data were analyzed using the Johnson–Mehl–Avrami–Kolmogorov (JMAK) method, and the Avrami's exponent \(n\) and rate constant \(k\) for each testing condition. The grain growth kinetics followed a power law behavior with an exponent coefficient \({n}_{g}\) and a Hall–Petch type relationship was found between the grain size and microhardness evolution. The results showed that the conventional JMAK equation could not accurately model the static softening kinetics of AA2024–T3. Moreover, the Avrami's exponent n and rate constant \(k\) determined from the modified JMAK equation containing an impingement parameter, the \({n}_{g}\) parameter from the grain growth power law and the Hall–Petch parameters were found to be different with the three directions. To validate the influence of plastic anisotropy on static softening, microstructure and microtexture characterization was carried out using a combination of Vickers microhardness tests, laser confocal microscopy, scanning electron microscopy, and electron backscatter diffraction before and after annealing.