Development of Fe-11Al-xMN alloy steel on cryogenic temperatures

This research is focused on increasing the reliability of Fe-11Al-Mn by combining the properties of Mn and the superiority of Fe-Al-C under cryogenic temperature. Three Fe-11Al-Mn alloys with compositions of 15 wt % Mn (F15), 20 wt % Mn (F20), and 25 wt % Mn (F25) were investigated. The cryogenic process uses liquid nitrogen in a temperature range of 0–196 °C. Hardness testing using the Vickers method and SEM was used to analyze the microstructure. X-ray diffraction (XRD) testing was conducted to ensure the Fe-11Al-Mn alloy phase and corrosion testing was carried out using the three-electrode cell polarization method. With the addition of Mn, the Vickers hardness of the Fe-11Al-Mn alloy decreased from 331.50 VHN at 15 wt % to 297.91 VHN at 25 wt %. The value of tensile strength and fracture elongation values were 742.21 MPa, 35.3 % EI; 789.03 MPa, 41.2 % EI; and 894.42 MPa, 50.2 % EI, for F15, F20, and F25, respectively. An important factor for improving the performance of cryogenic materials is the impact mechanism. The resulting impact toughness increased by 2.85 J/mm2 to 3.30 J/mm2 for F.15 and F25, respectively. The addition of the element Mn increases the corrosion resistance of the Fe-11Al-Mn alloy. The lowest corrosion rate occurs at 25 % wt Mn to 0.016 mm/year. Based on the results, the F25 alloy has the highest mechanical and corrosion resistance of the three types of alloys equivalent to SS 304 stainless steel. The microstructure of Fe-11Al-Mn alloy was similar between before and after cryogenic temperature treatment, this condition showed that the microstructure did not change during the process. From the overall results, the Fa-11Al-Mn alloy is a promising candidate for material applications working at cryogenic temperatures by optimizing the Mn content