The Influence of Cooling Rate on Solidification Microstructure of 254smo Super Austenitic Stainless Steel

The microstructure evolution of 254 super austenitic stainless steel at five typical cooling rates (6-1000 °C min -1 ) were observed by high temperature confocal scanning laser microscopy (HT-CSLM). The results showed that the solidification mode of 254SMO was austenite-ferrite type (AF mode). The solidification structure was obvious dendritic characteristic, and the secondary dendrite arm spacing (SDAS) decreased with the increase of the cooling rate. Ferrite transformation occured within austenite matrix during the cooling process after solidification. As the cooling rate increased, it first decreased and then exhibited a reverse effect, while the sigma phase variation was opposite to ferrite phase