Microstructure evolution of ferrite during intercritical deformation in low carbon microalloyed steels

Abstract

Effects of strain, deformation temperature and strain rate on microstructure evolution of ferrite during intercritical deformation in a low carbon microalloyed steel have been studied via electron back-scattered diffraction analysis. The result shows that continuous dynamic crystallisation (CDRX) can be induced by a small strain of 0.25 when deformation temperature is 750°C and strain rate is 0.1 s⁻¹. Increasing deformation temperature or reducing strain rate prompt the CDRX. However, CDRX is remarkably enhanced when deformation temperature is larger than 780°C even under large strain rate condition. Both the equiaxed grain sizes and sub-grain sizes of intercritically deformed microstructures are smaller than 3 μm at various process parameters. Intercritical deformation is an effect way to ultra-refine microstructure for steels.

KEYWORDS:

• Intercritical deformation
• ferrite
• continuous dynamic crystallisation
• electron back-scattered
• diffraction
• equiaxed ultrafine grains
• sub-grains
• local misorientation
• low carbon microalloyed steels

Acknowledgements

The authors greatly appreciate the equipment supports from the State Key Laboratory of Rolling and Automation, Northeastern University, China.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Xin-jun Shen http://orcid.org/0000-0002-0705-1260

Additional information

Funding

The financial supports from National Postdoctoral Program for Innovative Talents (BX201700301) and the Fundamental Researcher Funds for the Central Universities (N170703009) are gratefully acknowledged. The authors also acknowledge a research grant from China Postdoctoral Science Foundation (2018M631803).