Hot deformation behavior and microstructure evolution of each single phase in DSS

Abstract

This paper presents a systematic experimental study to clarify the relationship between the hot deformation conditions and microstructure evolution and flow stress of the individual ferrite and austenite phases of duplex stainless steels (DSS), and to quantitatively compare the deformation behaviors of each phase under the same hot working conditions. Single-phase steels with the ferrite and austenite chemistry of the phases in the DSS were prepared for this investigation. The microstructure evolution and deformation behavior of the individual phases were investigated in one-pass hot uniaxial compression tests up to a strain of 0.8 at a wide range of working temperatures from 1000 to 1250 °C and strain rates from 0.1 to 30.0 s−1. The compressed microstructures of each phase were investigated, and microstructure evolution maps were proposed to demonstrate the relationship between the compressed microstructure and deformation conditions. The flow curves of each phase were also analyzed quantitatively, showing that the ferrite phase had lower hot strength and a lower work hardening exponent n, and higher strain rate sensitivity m and temperature sensitivity A compared to the austenite phase. The strength ratio of each phase from early to late deformation was expressed using the Zener-Hollomon parameter, and equations and constants for the strength ratio of the phases were proposed.