Abstract
The isothermal transformation of ferrite to austenite in a carbon-free Fe-8%Cr alloy has been studied at temperatures above A3 point, and quantitative analyses of the kinetics of the transformation have been made. The main results are as follows:
(1) Austenite preferentially nucleates at ferrite grain boundary corners and grows with a constant velocity in all directions.
(2) The nucleation sites are saturated in the early stage of the transformation.
(3) The isothermal transformation behaviour of austenite can be expressed by a Johnson-Mehl type equation, and the reaction exponents have a value about 3 for all transformation temperatures.
(4) The kinetics is in good agreement with Cahn’s theory of grain boundary nucleated reactions.
