Microstructure Evolution in Directionally Solidified Fe–C–Mn–(Si) Peritectic Steels

Bridgman solidification experiments are carried out on Fe–C–Mn–Si peritectic steels to clarify how growth velocity ( V ) and alloy composition govern microstructural evolution. At velocities of 10–120 μm s −1 , the microstructures exhibit competitive growth between primary δ dendrites, are subsequently enveloped by γ ‐austenite in the interdendritic regions. The primary dendrite arm spacing (PDAS) decreases systematically with increasing V but coarsens unexpectedly at intermediate growth rates in the presence of silicon. Experimental measurements are benchmarked against PDAS scaling models to assess predictive accuracy. Particular attention is given to the role of Si in modifying interfacial morphology and mushy zone characteristics. The results demonstrate that elevated Si levels, when coupled with faster growth velocities, extend the mushy zone length and are associated with increased susceptibility to interdendritic solidification cracking. These findings provide mechanistic insight into crack formation in peritectic steels and highlight composition–processing interactions critical for continuous casting practice.