Research on Microstructures and Properties of High-Strength Anticorrosion Twinning-Induced Plasticity Steels

Abstract

The microstructures, mechanical properties, and anticorrosion properties of Fe–25Mn–Cr(12, 18 wt.%)–CN TWIP steels compared with nominal Fe–22Mn–0.6C TWIP steel (TWIP-ref) in the solid-solution state were investigated in the present study by using X-ray diffraction (XRD), electron backscattered diffraction (EBSD), transmission electron microscopy (TEM), tensile tests, and potentiodynamic polarization measurement, etc. The results show that the Fe–Mn–Cr–CN TWIP steels have excellent mechanical properties and anticorrosion properties compared to the TWIP-ref steel. The strain-hardening rate of the 12CrN steel is lower than that of the TWIP-ref steel because of the relatively late generation of high-density deformation twins, which resulted in less tensile strength increments during the tensile test. Moreover, M23C6 precipitates enriched with Mn and Fe formed in the Fe–Mn–Cr–CN steel as the Cr content increased, which had an important influence on the mechanical properties and anticorrosion properties. In the Fe–Mn–Cr–CN TWIP steels, because of the influence of the M23C6 precipitation in the 18CrN sample, the yield strength (σYS) is increased slightly, while the ultimate tensile strength (σUTS) and elongation to failure are decreased. In addition, 18CrN has poor corrosion resistance because of the formation of M23C6 precipitation (i.e., it has relatively negative corrosion potential (Ecorr) and a smaller corrosion current density (Icorr)).