The Defining Role of Plastic Deformation on Resistance to Aqueous Corrosion of Interstitial Free Steel

Thirty-five ‘apparently’ recrystallized specimens were produced through a combination of cold rolling and recrystallization annealing. They had a range of average grain size (d_av:18-467 μm), grain orientation spread (GOS: 0.31 to 1.24 deg) and volume fraction of ND||<111> (\({V}_{f}^{ND||<111>}\): 0.15-0.69). The GOS value, for individual grains or for an entire specimen, represented presence of ‘remnant’ cold work – existence of geometrically necessary dislocations and ‘minor’ orientation gradients. The resistance to aqueous corrosion was determined by this ‘remnant’ cold work, and not by average grain size or crystallographic texture. The role of mesoscopic distribution in plastic deformation, and the features of deformed microstructure, were then explored on the resistance to aqueous corrosion. Progressive plastic deformation, through laboratory cold rolling, brought reproducible non-monotonic corrosion responses. In particular, an increase in corrosion resistance (0 to 30 pct rolled) was followed by a drop (30-40 pct) and then an increase (> 40 pct rolling). These changes originated from the evolution in deformed microstructures: formation of near boundary orientation gradients and creation of low and high angle boundaries, respectively. A combination of microtexture and non-contact profilometry clearly established that deformation induced near boundary orientation gradients and grain-interior high angle grain boundaries provided resistance to aqueous corrosion, while low angle boundaries were detrimental.