Effect of grain refinement on tensile properties and electrochemical behavior of Fe-18.5%Cr ferritic stainless steel

Abstract

In the present study, the effect of grain refinement on mechanical properties and electrochemical behavior of Fe-18.5%Cr ferritic stainless was investigated using tensile testing and a series of electrochemical analyses. Results of tensile testing clearly showed that the yield and tensile strength of material are improved by grain refinement but the uniform and total elongations are inversely affected. The true stress-strain curves were modeled using Hollomon equation. It was concluded that the coarse and fine grained samples represent a two stage strain hardening behavior and the reason for these observations was discussed. The electrochemical studies using open circuit potential measurement showed that the fine-grained sample has higher values of OCP than the coarse-grained one. In addition, the potentiodynamic polarization curves for these two types of microstructures demonstrated similar trends. It was also observed that grain refinement decreases the corrosion current density and increases the corrosion potential. Electrochemical impedance spectroscopy (EIS) analysis revealed that grain refinement increases the polarization resistance of ferritic stainless steel. Finally, it was deduced that the corrosion and passivation behavior of the ferritic stainless steel in the 0.1 M HNO3 solution are improved by refining the grain structure by thermo-mechanical processing.