Improved recrystallization resistance by ferrite and carbide in a ferritic/martensitic (F/M) steel

To ensure long-term thermal stability of deformed materials, 9–12 %Cr ferritic/martensitic (F/M) steels require exceptional resistance to recrystallize. Here we proposed a dual-phase strategy on a 9Cr F/M steel with high-density carbides by adjusting Si and C content. The designed 9Cr–1Si-0.12C steel (1Si) exhibits a 102 °C increase in recrystallization temperature (from 655 °C to 757 °C under 50 % cold rolling deformation) compared to the conventional 9Cr-0.2Si-0.06C steel (0.2Si). This enhancement originates from synergistic effect of carbides and ferrite: (i) a high density of carbides impedes bulge nucleation in martensite; (ii) soft ferrite accommodates mass deformation through geometric necessary dislocations (GNDs) accumulation, reducing the stored energy of martensite; (iii) fence-like ferrites decorated with carbides sever as natural barriers to restrict the growth of martensite effectively, increasing the energy consumption of recrystallization. In addition, the recrystallization of ferrite is also limited by the formation of high-density thermal-stable GNDs and high-content low-energy rotated cube texture.