| dc.description | The present work has studied the kinetics of partial reversion of martensite into austenite, which
occurred during overaging between 520 and 600??C in a maraging 350 steel. The microstructural modifications
were followed using optical microscopy, scanning electron microscopy, X-ray diffraction and ferritoscopy.
The observations carried out using microscopy showed that the reverted austenite is formed at
interface regions such as grain boundaries, boundaries of the packets and martensite laths boundaries of
the martensitic structure starting at 520??C, while the reverted austenite observed inside the martensite
lath was formed starting at 560??C. The maximum percentage volumetric fractions of retained austenite
were 18%, 25% and 37%, respectively for 520, 560 and 600??C. The higher the aging temperature, the
faster the volumetric fraction attained its plateau of maximum constant value. The activation energy for
the kinetics of the austenite reversion process has been determined as being 332 kJ/mol. The Avrami
constant for the kinetics of the reverted austenite at 520??C was close to 1, while at 560??C was close to
2. The values determined for the activation energy and of the Avrami constants have been discussed and
correlated with the possible transformation mechanisms. | |
