Acceleration of Spheroidization in Low-Density Ultrafine Pearlitic Steel by κ-Carbide

作者：Chen, Ming; Zhang, Chen; Zhang, Guohong^*; Zhou, Jie; Hu, Feng^*; Wu, Kaiming

来源：Steel Research International, 2024.

DOI：10.1002/srin.202300564

• lamellar spacings
• low-density steels
• spheroidization
• ultrafine pearlites
• kappa-carbides

The impact of kappa-carbide on the spheroidization process of low-density ultrafine pearlitic steel (with 5 wt% Al and 5 wt% Mn additions) is investigated through isothermal annealing spheroidization. In the findings, it is demonstrated that kappa-carbides can significantly refine the lamellar spacing of low-density ultrafine pearlite during the isothermal transformation. Additionally, under identical conditions, kappa-pearlite exhibits a higher number of ferrite/kappa-carbide interfaces. In the first stage of pearlite spheroidization, an abundance of dislocations and sub-grain boundaries facilitate rapid fusion of the lamellar pearlite, while in the second stage, they provide a high-speed diffusion pathway for carbon diffusion. Moreover, the reduced lamellar spacing shortens the distance for carbon and alloying elements diffusion, thereby promoting granular kappa-carbide formation and accelerating spheroidization in low-density ultra-fine pearlite.