Effect of thermomechanical processing via rotary swaging on grain boundary character distribution and intergranular corrosion in 304 austenitic stainless steel

In the present work, the thermomechanical processing consisting of rotary swaging deformation and annealing treatment was performed to optimize the grain boundary character distribution (GBCD) of 304 austenitic stainless steel. To systematically investigate the effect of GBCD evolution on intergranular corrosion (IGC), double loop electrochemical potentiokinetic reactivation and electrolytic oxalic acid etch tests were employed. The experimental results show that the fraction of low-1 coincident site lattice (CSL) boundaries increased from 58.1% to 74.0% for the specimen swaged to 0.06 true strain and then annealed at 1050 degrees C for 5 min duration. By characterizing the evolution of GBCD as a function of strain level in terms of low-1 CSL boundaries fraction, average twin-related domain (TRD) size, average number of grain per TRD and fractal dimension of the maximum random boundary connectivity, the grain boundary engineering (GBE) microstructure was realized by the occurrence of prolific multiple twinning events during strain-induced boundary migration while static recrystallization has a detrimental effect on optimizing GBCD for the prolific of new strain-free grains with random boundaries. The IGC resistance of the GBE-treated 304 austenitic stainless steel is enhanced by inhibiting the nucleation and propagation of IGC cracks, resulting from the increase in the fraction of low-1 CSL boundaries, especially Sigma 3 boundaries and the disruption of random boundary network connectivity. (C) 2022 The Author(s). Published by Elsevier B.V.

Automated summary

In this study, thermomechanical processing was used to optimize the grain boundary character distribution (GBCD) of 304 austenitic stainless steel. The effect of GBCD evolution on intergranular corrosion (IGC) was investigated, and the results showed that the increase in low-1 coincident site lattice (CSL) boundaries improved the corrosion resistance of the steel.