Softening behaviour of Fe-6.5%Si steel during warm deformation process

State Key Laboratory of Rolling and Automation, Northeastern University, 110819 Shenyang, PR China

^a Corresponding author: e-mail: lics@ral.neu.edu.cn

Abstract

To investigate the softening behaviour during warm deformation process, thermal compression experiment of Fe-6.5%Si silicon steel was conducted. To study the relationship between stress and strain at different strain rate, the investigation of the microstructure, hardness as well as ordered phase constituent of the rolled parts was carried out, respectively. At strain less than or equal to 0.3, micro-hardness was observed to increase with increasing strain. For strain greater than 0.3, the micro-hardness decreased with increasing strain. Indentation morphology of Vickers hardness reveals that the sink-in deformation occurs as the steel has a higher strain-hardening exponent, while pile-up deformation takes place at a lower strain-hardening exponent. Brittle B₂ (FeSi) and DO₃ (Fe₃Si) ordered phases exists in Fe-6.5%Si steel. With the increasing strain, the diffraction spot strength of B₂ and DO₃ ordered phase is decreased, resulting in the softening behaviour of the Fe-6.5%Si steel during warm deformation process.