LAUSR

Abstract We elucidate here the morphological evolution of reverted austenite in a newly designed cobalt-free maraging steel and its significance in predicting the mechanical behavior. Three distinct types of reverted austenite, granular reverted austenite at grain boundaries (γG1), lamellar reverted austenite in the matrix (γL) and globular reverted austenite (γG2) were observed, depending on the aging temperature and time. At low temperatures (560 °C and 640 °C), only γG1 and γL were observed. While at relatively high temperature (700 °C), γG1 and γL decreased with the increase of holding time and were completely transformed to γG2 at equilibrium condition. The observation of three different morphologies of reverted austenite are envisaged to be a consequence of competition between the nucleation rate and growth rate of reverted austenite at different aging temperatures. The weak texture of maraging steel with high Schmid factor at high aging temperature implied that γL and γG2 are the reasons for superior toughness and ductility. The present study of nature of austenite is also of significant interest in next generation of advanced high strength steels because of its remarkable effect on ductility.