Effect of cooling rate on solidification microstructures in AISI 304 stainless steel.

AISI 304 austenitic stainless steel was cast into a water cooled copper mould with wedge shaped slot to investigate the effect of cooling rates on its microstructural evolution and solidification sequences between δ ferrite and austenite phases. Dendritic δ ferrite forms at the base of the sample where the cooling rate is low. With increasing cooling rate, the solidification mode is transformed from primary ferrite mode to primary austenite mode resulted from the phase selection. The metastable austenite solidifies as the primary phase due to its kinetic advantage when the growth rate is sufficiently high. With the higher cooling rate at the tip of the sample, the morphology of the austenite phase transforms from dendritic to cellular. [ABSTRACT FROM AUTHOR]