Hard Bainite

H. K. D. H. Bhadeshia

Abstract

It is possible to create bainite in the form of long, slender crystals of ferrite whose scale compares with that of carbon nanotubes. These crystals are about 200 Å in thickness and are generated by the partial transformation of austenite. The result is an extraordinary combination of strength and toughness; the bainite has the highest hardness and lowest transformation temperature ever reported. The mechanism of transformation is such that a stable carbon concentration which is many orders of magnitude greater than its equilibrium solubility, is retained in the ferrite in spite of aggressive tempering heat--treatments. All this can be achieved in bulk steel and without the use of expensive solutes, deformation or rapid thermal treatments. The science associated with this bainite is described, together with a series of characterisation experiments ranging from atoms to the behaviour of large components in violent deformation.

Solid→Solid Phase Transformations in Inorganic Materials, Edited by J. M. Howe, D. E. Laughlin, J. K. Lee, U. Dahmen and W. A. Soffa, 2005, Volume 1, pages 469-484.

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