Composition Design of Nanocrystalline Bainitic Steels by Diffusionless Solid Reaction

NANOBAIN is the term used to refer to a new generation of advanced steels capable of producing by isothermal transformation at low homologous temperatures, T/T-m similar to 0.25 where T-m is the absolute melting temperature, a nanocrystalline microstructure, composed exclusively of two phases, thin plates of bainitic ferrite separated by C enriched austenite. Such alloys are exclusively designed on the basis of bainitic transformation theory and some physical metallurgy principles. In this work, by designing a new set of alloys capable of producing such microstructure, a further step toward the industrialization of NANOBAIN is taken. Some important industrial requirements, including circumventing the inclusion of expensive alloying elements and the need for faster transformations, are also considered. For all the alloys, the experimental results validate the design procedure and they illustrate that the NANOBAIN concept is a step closer to industrialization, probing that it is possible to obtain nanocristalline bainite in simpler alloy systems and in shorter times than those reported previously.