Theoretical design and advanced microstructure in super high strength steels

A theoretical design procedure based on phase transformation theory alone has been successfully applied to design steels with a microstructure consisting of a mixture of bainitic ferrite and retained austenite. Using thermodynamics and kinetics models, a set of four carbide free bainitic steels with...

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Bibliographic Details
Published in:Materials in engineering 2009-06, Vol.30 (6), p.2077-2083
Main Authors: Caballero, F.G., Santofimia, M.J., García-Mateo, C., Chao, J., de Andrés, C. García
Format: Article
Language:English
Subjects:
Ferrous metals and alloys
Mechanical properties
Microstructure
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Summary:A theoretical design procedure based on phase transformation theory alone has been successfully applied to design steels with a microstructure consisting of a mixture of bainitic ferrite and retained austenite. Using thermodynamics and kinetics models, a set of four carbide free bainitic steels with a 0.3 wt.% carbon content were designed and manufactured following a thermomechanical treatment consisting of hot rolling and two-step cooling. The designed steels present significant combinations of strength and ductility, with tensile strengths ranging from 1500 to 1800 MPa and total elongations over 15%. However, a carbon content of 0.3 wt.% is still high for in-use properties such as weldability. In this sense, a reduction in the average carbon content of advanced bainitic steels was proposed. Improved bainitic steels with a carbon content of 0.2 wt.% reached combinations of strength and ductility comparable to those in TRIP assisted steels.
ISSN:0261-3069
DOI:10.1016/j.matdes.2008.08.042