Effect of Transformation Temperature on Microstructure and Retained Austenite in a Fast-Transforming Carbide-Free Bainitic Steel
摘要
Developing carbide-free bainitic steels suitable for industrial continuous annealing demands compositions capable of transforming within short thermal cycles. In a previous study, the influence of chemical composition on the required transformation time was investigated. The present work analyzes the effect of transformation temperature on the fastest-reacting alloy and demonstrates a computationally guided design strategy to accelerate bainitic kinetics in a low-Mn steel. Isothermal treatments were performed at 350, 400, and 450 °C (20–600 s). Microstructural analysis confirmed the formation of carbide-free bainitic ferrite and stabilized retained austenite, reaching ~ 15% at 350 °C. The alloy achieved a strength–ductility combination characteristic of third-generation AHSS (UTS ≈ 1160 MPa, elongation ≈ 28%). These results confirm that rational alloy design enables short-cycle production of these steels for industrial applications.