Study of Intercritical Annealing in Air-Cooled Fe-Mn-Al-C Lightweight Forging Steel for Tailoring the Mechanical Properties

Herein, the opportunity of lightweight medium-manganese steel Fe-7Mn-6Al-0.3C for forged components produced without quenching and tempering treatments is explored. The selected composition reveals neither cracks nor intergranular coarse kappa-carbide and has a lower density than pure iron by 9%. Despite the massive dimension of the forged bar and decreased thermal conductivity, outstanding mechanical properties can be achieved by air-cooling followed by intercritical annealing. An intermediate tensile strength of 685 MPa with total elongation of 29% can be achieved by annealing at 800 degrees C for 1,000 s, whereas an ultimate tensile strength above 1,000 MPa with an elongation of 13% can be reached by forming tempered martensite with fine kappa-carbide at 400 degrees C.