Manipulating Precipitation Through Thermomechanical Treatment to Control Corrosion Behavior of an Al-Cu-Mg Alloy

Controlling the precipitation through thermomechanical treatment is an important method to improve the corrosion resistance of Al-Cu-Mg alloys. In this study, the corrosion behaviors of Al-Cu-Mg alloys in the solution-treated state and retrogression-treated state under cold rolling deformation and then natural aging were investigated. In the solution-treated series alloys, the cold-rolled deformation improved the resistance to intergranular corrosion by suppressing the precipitation of the S-phase on the grain boundaries. The increased pitting potential and corrosion potential were related to the increased concentration of solute atoms within the grain interiors and the eliminated S-phase on grain boundaries. In the retrogression-treated series alloys, the 30% cold rolling deformation stimulated the growth of the S-phase and transformed the S-phase distribution from discontinuous to continuous on the grain boundaries, thereby changing the pitting corrosion to the network corrosion morphology. The precipitation of the S-phase with large dimension within the grain interiors contributed to the decreased pitting potential and corrosion potential.