Interphase and fibrous precipitation in a thermomechanically processed V–Nb–Mo microalloyed steel

Abstract

A novel V–Nb–Mo steel was thermomechanically processed to promote ferrite grain refinement and precipitation during the austenite to ferrite transformation. Transmission electron microscopy and three-dimensional atom probe tomography confirmed the formation of two main types of precipitates: nano-scale interphase precipitates and fibrous precipitates (FP). Both the precipitates had a Baker–Nutting orientation relationship with the ferrite matrix, but with different variants. Interphase precipitates exhibited a disc shape with an average distance between precipitate rows of 15 ± 2 nm and an average Guinier radius of 3.9 ± 1.7 nm, whereas FP had a rod-shape 2.5 ± 0.5 nm in radius and 8–25 nm in length. It appeared that the FP are formed along the plane perpendicular to the interphase precipitates plane.

KEYWORDS:

• Interphase precipitates
• fibrous precipitates
• thermomechanical simulation
• TEM
• APT

Acknowledgements

The authors would like to acknowledge the scientific support of the Advanced Materials & Characterization Research Group, R&D Tata Steel Limited. Deakin University’s Advanced Characterisation Facility is acknowledged for use of the TEM and APT. The authors are grateful to R&D Tata Steel management for allowing this work to publish.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The raw/processed data required to reproduce these findings cannot be shared at this time as the data also form part of a continuing study.