Bainite to austenite transformation

Proceedings of an International Conference: Phase Transformations '87, Institute of Metals, London, Edited by G. W. Lorimer, 1988, pp. 203-206, by J. R. Yang and H.K.D.H. Bhadeshia

This research paper investigates the isothermal reaustenitisation process in steel, specifically examining how bainitic ferrite transforms back into austenite through diffusional growth. The study utilises a homogeneous alloy to analyse why this transformation occurs only after reaching specific thermal thresholds, as the initial bainite reaction typically halts before reaching equilibrium.

Through dilatometric experiments and theoretical modelling, the authors demonstrate that the degree of transformation increases with temperature until a fully austenitic state is achieved. The findings highlight that alloying element redistribution occurs during this phase change, moving toward a state of paraequilibrium at lower temperatures.

Ultimately, the work provides a theoretical framework to predict how the volume fraction of austenite evolves based on the carbon concentration and the phase diagram of the material.