Dissolution Kinetics of Fe‐Rich Phases and Its Impact on the Dual‐Blockage Corrosion Mechanism in 7075 Aluminum Alloy During Isothermal and Nonisothermal Solution Treatments

This study compared the effects of isothermal and nonisothermal solution treatments on the microstructure and corrosion resistance of 7075 aluminum alloy. Microstructural evolution was characterized by differential scanning calorimetry (DSC), scanning electron microscopy with energy‐dispersive spectroscopy (SEM/EDS), and optical microscopy (OM), while corrosion behavior was evaluated by intergranular corrosion (IGC) immersion and potentiodynamic polarization tests. Nonisothermal continuous heating to 570 °C provided sustained thermal energy that promoted pronounced refinement and dissolution of coarse Al 7 Cu 2 Fe particles by overcoming their high activation‐energy barrier. Based on the nonisothermal Johnson–Mehl–Avrami–Kolmogorov (JMAK) kinetic model, the dissolution of the second phase was revealed to exhibit a threshold‐triggered characteristic (Avrami exponent n ≈ 4.3), with its area fraction experiencing a precipitous decline and approaching a thermodynamic limit of 0.48%. This microstructural evolution improves the corrosion resistance of the alloy: the electrochemical corrosion current density is reduced by approximately 67%, and the maximum IGC depth transitions from deep penetrative fissures to shallow surface pits. Accordingly, an electrochemical and grain boundary dual‐blockage corrosion model is proposed. This strategy suppresses surface microgalvanic corrosion by reducing the cathodic area and disrupting continuous anodic pathways along grain boundaries. This study provides insights into heat‐treatment corrosion mitigation in high‐strength aluminum alloys.