Heat Treatment And Corrosion Performance Of Fe-Mn-Al-C Steel

Fe-Mn-Al-C steel is widely used in the automotive and equipment manufacturing fields as a low density and excellent mechanical performance steel.With the continuous optimization of composition by scholars,the corrosion resistance of Fe-Mn-Al-C steel has improved,making it possible for this steel to be applied in the marine field.This study conducted heat treatment on low density steel with Fe-25Mn-10Al-0.7C composition.The corrosion behavior and electrochemical corrosion performance of the steel under different processes were studied using analysis and testing methods such as metallographic microscope microstructure analysis,scanning electron microscope morphology analysis,X-ray diffraction analysis,energy spectrum analysis,and electrochemical corrosion analysis.The sample has undergone solid solution,quenching,and tempering heat treatment,resulting in a dual phase structure of austenite and ferrite.According to neutral salt spray corrosion and SEM analysis,the corrosion products first grow laterally on the surface and then grow longitudinally above the substrate,resulting in various corrosion products with different densities;EDS analysis shows that the corrosion of this steel type mainly starts from pitting corrosion,which is mainly caused by element segregation;The main products analyzed by XRD include Fe₂O₃,Mn₃O₄,Al₂O₃,Fe₃O₄,Fe OOH,etc.Electrochemical analysis shows that as the corrosion products are generated to cover the surface of the substrate,the corrosion potential first moves in a positive direction and then moves in a negative direction,resulting in more obvious pitting corrosion.The dense corrosion products partially protect the substrate,while the production of loose Mn oxides exacerbates the corrosion situation.In this study,the samples were aged at different temperatures for 168h.XRD results showed that B2 and DO3 phases were produced after 48h of low temperature aging,more B2 and DO3 phases were produced during middle temperature aging compared with low temperature aging,andκ-carbide appeared during high temperature aging for a longer time.The electrochemical analysis shows that a small amount of B2 is beneficial to the corrosion resistance of the steel,and too much DO3 is unfavorable to the corrosion resistance of the steel.The production ofκ-carbide is also unfavorable to the corrosion resistance of the steel.