Microstructure evolution in ferritic stainless steels during large strain deformation

作者：Belyakov A^*; Kimura Y; Adachi Y; Tsuzaki K

来源：Materials Transactions, 2004, 45(9): 2812-2821.

DOI：10.2320/matertrans.45.2812

• ferritic stainless steels
• severe plastic deformation
• strain hardening
• grain refinement
• grain boundaries
• internal stress

Deformation microstructures were studied in ferritic stainless steels during cold bar rolling and swaging to total true strains about 7. Two steels, i.e. Fe-22Cr-3Ni and Fe-18Cr-7Ni with coarse-grained ferritic and fine-grained martensitic initial microstructures, respectively, were selected as starting materials. Microstructure evolution in the both steels was characterized by the development of highly elongated (sub)grains aligned along the rolling/swaging axis. The transverse size of these (sub)grains in the Fe-22Cr-3Ni steel gradually decreased to about 0.1 mum with increasing the strain. On the other hand, the transverse (sub)grain size in the Fe-18Cr-7Ni steel decreased to its minimal value of 0.07 mum with straining to about 3 followed by a little coarsening under further working. The strengthening of worked steels that revealed by hardness tests correlated with the microstructure evolution. The hardness of the Fe-22Cr-3Ni steel increased with cold working within the studied strain range, while that of the Fe-18Cr-7Ni approached a saturation after fast work hardening at strains below 3, leading to an apparent steady-state behaviour. Development of strain-induced (sub)grain boundaries and internal stresses in the steels with different initial microstructures during severe deformation is discussed in some detail.

• 出版日期2004-9