Banded microstructure in a low-alloyed eutectoid steel

ABSTRACT

The possible influence of banded microstructure on the fracture performance of a high-carbon steel is investigated using electron microscopy and X-ray diffraction techniques. The banded microstructure was found to be alternating layers of bainite and tempered martensite/retained austenite. Transformation of bainite was promoted by a combined effect of segregation of alloying elements, non-uniform thermal gradient across the steel, and the insufficient austenitisation. The transformation of bainite along the prior austenite grain boundaries (PAGBs) introduces a non-uniform strain distribution at bainite/martensite interface and a higher stress concentration, which may eventually lead to the failure of the heavy section in a brittle intergranular manner. Results provide insights to the importance of understanding the bainitic transformation in such eutectoid steel systems.

KEYWORDS:

• Hypereutectoid steel
• heavy section
• bainite
• segregation
• fracture

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Rangasayee Kannan http://orcid.org/0000-0002-5792-5739

Yiyu Wang http://orcid.org/0000-0001-7248-0646

Leijun Li http://orcid.org/0000-0003-2411-3846