A Methodology for the Prediction of Time-Temperature-Transformatios Diagrams

J. L. Lee and H. K. D. H. Bhadeshia

Abstract

A method based on nucleation theory but using fitted constants was used to model the time-temperature-transformation (TTT) diagrams of steels. The transformation-start C-curves on the diagrams were represented as functions of the free energy of nucleation and of an activation energy. The subsequent increase in volume fraction with time is treated using the Johnson-Mehl- Avrami equation. These results, and published methods for determination of the variety of transformation-start temperatures, are demonstrated to estimate properly the published TTT diagrams for a large variety of commercial steels containing C, Mn, Si, Ni, Mo and Cr as solute additions.

Materials Science and Engineering A 1993, Vol.171, No.1- 2, pp.223-230

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