In this study, we investigated the transformation kinetics of martensite → reverted austenite in 18 wt.% grade 300 Ni maraging steel. The kinetics was evaluated based on the in situ synchrotron x-ray diffraction data collected during isothermal heat treatment at 570°C. The onset of transformation martensite → reverted austenite was detected after ~ 5 min of aging. The austenite fraction increased as a function ...