Influence of Heat Treatment Temperature on the Electrochemical Properties of Cold-Rolled 0.2%C–3%Al–6/8.5%Mn–Fe Medium Manganese Steel

The microstructure evolution, polarization curve and impedance of cold-rolled 0.2%C–3%Al–6/8.5%Mn–Fe steel under heat treatment temperatures of 600–800 ℃ holding 10 minutes were tested. The results show that the cold-rolled texture of the steel does not completely disappear at 600 ℃ and 650 ℃, exhibiting high charge transfer resistance Rc and corresponding corrosion potential Ecorr. When the heat treatment temperature rises to 700 ℃, the texture begins to eliminate, the Rc begins to decrease, indicating a decrease in corrosion resistance. When the heat treatment temperature rises to 750 ℃ and 800 ℃, it can be found that the proportion of austenite begins to increase and the number of grain boundaries decrease, resulting in an increase in Rc and an improvement in the corrosion resistance of the steel. Compared to 6.5Mn steel, the higher Mn content in 8.5Mn steel results in better corrosion resistance after high-temperature heat treatment.