Effect of Annealing Temperature on the Microstructure, Tensile Properties, and Fracture Behavior of Cold-Rolled High-Mn Light-Weight Steels

The effects of the annealing temperature on the microstructure and tensile properties of cold-rolled light-weight steels are investigated using two Fe-30Mn-xAl-0.9Calloys that contain different Al content.The initial alloy microstructure is composed of a single austenite or a mixture of austenite and ferrite depending on the nominal aluminum content.For the alloy with 9 wt% Al content, the recrystallization and grain growth of austenite occurrs depending on the annealing temperature.However, for the alloy with 11 wt% Al content, the β-Mn phase is observed after annealing for 10 min at 550~800 ℃.The β-Mn transformation kinetics is the fastest at 700 ℃.The formation of the β-Mn phase has a detrimental effect on the ductility, and this leads to significant decreases in the total elongation.The same alloy also forms κ-carbide and DO3 ordering at 550~900 ℃.The investigated alloys exhibit a fully recrystallized microstructure after annealing at 900 ℃ for 10 min, which results in a high total elongation of 25~55% with a high tensile strength of 900~1170 MPa.