Synchronous optimization of strengths, ductility and corrosion resistances of bulk nanocrystalline 304 stainless steel

Abstract

Structural materials usually suffer from several attacks during their service, such as tension, fatigue and corrosion. It is necessary to synchronously improve these properties for their lightweight and long-lifetime, but corrosion resistance and ductility are generally inverse correlation with strength, it is very difficult to simultaneously optimize all three properties. However, bulk nanocrystalline 304 stainless steel (BN-304SS) produced by severe rolling technology possessed the larger yield and ultimate tensile strengths with sufficient elongation (> 40%) during tensile test, the larger saturation stress and longer lifetime during low-cycle fatigue, the enhanced uniform and pitting corrosion resistances during five-day immersion test in 6 mol/L HCl, the lowered stress corrosion cracking (SCC) susceptibility with larger yield (∾2.40 GPa) and ultimate tensile (∾2.66 GPa) strengths, and enough elongation (> 30%) during stress corrosion in comparison with conventional polycrystalline 304 stainless steel (CP-304SS) counterpart. The uniform and pitting corrosion resistances of fractured BN-304SS were enhanced in comprsion with those of fractured CP-304SS during seven-day immersion test in 1 mol/L HCl. These results demonstrated the strengths, ductility and corrosion resistances of BN-304SS can be simultaneously optimized by severe rolling technology. These improved results of BN-304SS in different disciplines were understood by its valence electron configurations rather than traditional microstructural parameters.