Effect of Mn content on mechanical and anti-corrosion property of Fe-7Cr-xMn steels

This study systematically investigates the effects of the Mn content on the microstructural evolution, mechanical properties and corrosion behavior of Fe-7Cr-xMn (x = 0-8, at.%) alloys. The microstructure was characterized using X-ray diffraction, scanning electron microscopy and electron backscatter diffraction. The tensile properties of the alloys were measured and strengthening mechanisms were analyzed. Electrochemical tests were performed and corrosion surface morphology and products were characterized. The results show that the addition of Mn significantly refines the microstructure of the alloys, particularly reduces the sizes of the martensite. The strength of the alloys is improved by the addition of Mn. The refinement of the microstructure is the main contributor to the improvement of the strength. According to the electrochemical tests, the corrosion properties do not change significantly when the Mn content is low. However, the corrosion current and pitting potential decreases significantly, and the alloy transitions from pitting corrosion to uniform corrosion when the Mn content reaches 8 at.%, indicating a significant decrease in corrosion resistance. Therefore, it is promising that the mechanical properties may be improved with minimal loss in corrosion resistance by the optimization of the Mn content in Fe-7Cr-xMn alloys.