Effect of silicon on the hot deformation behavior of microalloyed TWIP-type stainless steels

Publication date: 15 September 2018
Source:Materials & Design, Volume 154
Author(s): Atef Hamada, Timo Juuti, Ali Khosravifard, Anna Kisko, Pentti Karjalainen, David Porter, Jukka Kömi
In the present study, two vanadium-microalloyed 10Mn-18Cr TWIP-type stainless steels with low and high Si contents were designed to achieve a stacking fault energy of 25 mJ/m². Hot deformation behavior was investigated using compression tests in the temperature range 950–1100 °C and strain rate range 0.01–10 s⁻¹. Microstructural features of the rolled slabs were studied using optical microscopy and those of the hot deformed specimens by electron backscatter diffraction. The low-Si steel possessed a higher hot deformation resistance and a higher activation energy of deformation (507 kJ/mol) compared to the high-Si steel (477 kJ/mol). This unusual trend is attributed to an increasing fraction of soft ferrite in the latter steel with increasing temperature. At lower test temperatures, where partial dynamic recrystallization occurred in the high-Si steel, ferrite possessed high-angle grain boundaries, while the austenite contained dislocation substructures. The hot deformation behavior of the steels was modeled using the dislocation density based Bergström model and the dynamic recrystallization based Avrami model. The rate of increase of Bergstrom's hardening parameter as a function of the Zener-Hollomon parameter is seen to be higher for the high-Si steel.

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