Effect of plastic deformation on the precipitation reaction in 2024 alloys

The plastic deformation effect on activation energy, transformed volume fraction, and Avrami exponent for the phase precipitation in a 2024 aluminum alloy was evaluated in this study. Differential scanning calorimetry characterization was carried out in deformed and non-deformed samples, focusing on the study of S phase precipitation (Al2CuMg precipitates with orthorhombic structure, space group Cmcm, and lattice parameters a = 4.03 Å, b = 9.3 Å, c = 7.08 Å). The results show that the solid-state reactions were activated, kinetically controlled, and modified by the plastic deformation. The enthalpy changes, activation energy, and peak temperature shifting confirm that the applied deformation alters the reaction sequence. Two different Avrami exponent values were found, one close to 1.7, which indicates that nucleation occurs in preexisting nucleation sites, and the other near 1.3, which corresponds to phase transformation driven by diffusion mechanisms. •The S-phase precipitation was thermally activated and kinetically controlled.•%ε modify the ΔH, Tp, and Q but does not affect the precipitation sequence.•Avrami exponent ~1.7 indicated that nucleation occurs in preexisting sites.•Avrami exponent ~1.3 showed that phase transformation is driven by diffusion.