Kinetics and Microstructural Control

Isothermal Transformations

· Following a phase transition as a function of time at selected transformation temperatures gives curves of the form shown.
· A given transformation-time curve can be described by the Avrami equation:
y = {1 - exp(-Ktn)},
where K, and n are constants
· The transformation rate, r(T), can be characterized by the 50% transformation point t0.5:
r(T) = (1/ t0.5 )

From: Guy, "Elements of Physical Metallurgy." Addison Wesley (1974)