Tempering Effects on the Stability of Retained Austenite and Mechanical Properties in a Medium Manganese Steel

Abstract

Tempering effects on the austenite stability and mechanical properties of 0.2C–5Mn steel were investigated in the temperature range from 100°C to 600°C with 1 hour. It was found that tempering doesn't result in a significant change of the austenite plus ferrite duplex structure, which was developed in the previous annealing through austenite reverted transformation, whereas significant decreasing of the austenite fraction and carbon concentration was found in the specimens tempered at 200°C and 500°C due to the precipitation of carbides. Correspondingly tempering slightly deteriorates the ductility when the specimens were tempered at 200°C and 500°C without effects on mechanical properties around 400°C. Based on the analysis of relationship between mechanical properties and retained austenite, it was found that the product of tensile strength to total elongation (Rm*AT) was strongly dependent on the product of the volume fraction and carbon concentration of retained austenite (fA*Cγ). Furthermore, the optimal mechanical properties with tensile strength 1000 MPa and total elongation 40% could be obtained after tempering at 400°C with 1 hour, which means that galvanization is feasible in the 0.2C–5Mn steel with ferrite and austenite duplex structure.