Improving the intergranular corrosion resistance of 304 stainless steel by grain boundary network control

The grain boundary network (GBN) was controlled by grain boundary engineering (GBE) in a 304 stainless steel. The total length proportion of Σ3n coincidence site lattice (CSL) boundaries was increased to more than 70% associating with the formation of large size highly twinned grain-cluster microstructure. Only coherent twin boundaries (Σ3c) were found to be resistant to intergranular corrosion (IGC) and only such boundaries could be termed “special” ones. The improvement of resistance to IGC of the GBE specimen can be attributed to the large size grain-clusters associated with high proportion of the Σ3n boundaries and the interconnected Σ3n-type triple junctions.

Research highlights
► The large size twin-induced grain-clusters constitute the grain boundary network.
► Only Σ3c boundaries were found to be resistance to intergranular corrosion (IGC).
► The improvement of resistance to IGC is due to the large size highly twinned grain-clusters.