Impact of ultrafine-grained microstructure on the corrosion of aluminium alloy AA2024

Ultrafine-grained microstructures produced by severe plastic deformation upon AA2024-T351 were investigated with respect to pitting and intergranular corrosion. Refined microstructures were achieved using multiple pass equal-channel angular pressing (ECAP). Polarization in 0.5 M NaCl indicates that anodic behavior is affected by deformation when compared with coarse-grained specimens. Susceptibility to intergranular corrosion (IGC) via potentiostatic experiments reveals differences in the corrosion morphology between specimens with varying degrees of processing. In the unrefined state, IGC primarily occurs along grain boundaries; whilst ECAP processing predominantly results in pitting corrosion owing to a complete rearrangement of grain boundaries, revealing a desensitization effect arising from processing.

► Successful grain size reduction of an aircraft alloy.
► Transition from IGC to pitting.
► Newly generated grain boundaries are not prone to IGC.
► ECAP processing “desensitizes” grain boundaries.