Superior combination of strength and ductility in Fe–10Mn-0.6C steel trigged by austenite reversion transformation

Abstract

Austenite reversion transformation process was employed on Fe–10Mn-0.6C steel to adjust the content and stability of austenite and the transformation-induced plasticity effect was effectively improved. With increasing annealing temperatures from 550 °C to 590 °C and 620 °C, the content and proportion of lath-like austenite significantly increased. Austenite exhibited different stability after annealing at different temperatures, mainly related to the distribution of Mn and C. The higher the local Mn and C concentration, the more stable austenite, vice versa. After annealing at 620 °C for 6 h, the highest austenite content of 61 % was achieved, and half of that had a lath-like morphology. The steel had a superior combination of ultimate tensile strength of 1500 MPa and elongation of 59 %, resulting from the enhanced transformation-induced plasticity effect. The key reason was the alternating distributions of austenite and ferrite laths, accompanied with the formation of nanotwins in the austenite with high stability.