Different crystal growth and microsegregation mechanisms based on interface evolution in 0Cr18Ni9 stainless steel ingot

• The distribution of δ ferrite is caused by the microsegregation in solidification.
• The δ ferrite and microsegregation reveal the complicate crystal growth behaviors.
• The discrete crystal growth can happen in a scale smaller than the dendrite arm.
• The mechanism for diverse crystal growth is explained based on interface evolution.

Through the microstructure characterization, the different microsegregation and crystal growth phenomena were revealed in a 0Cr18Ni9 stainless steel ingot. Because the solute redistribution is slight in the step growth of δ ferrite-austenite transition, the different distribution of residual δ ferrite, which are depended on the solute segregation, should be traced back to the microsegregation in solidification. And the residual δ ferrite traced back to microsegregation in solidification further implies the complicate crystal growth behaviors. Under different solidification conditions, the shape and forward direction of crystal interface are different. Especially, the discrete crystal growth can happen in a scale smaller than dendrite grains and dendrite stems. The underlying mechanism for discrete crystal growth is explained based on interface evolution. Finally, the effect of different crystal growth behaviors on microsegregation is analyzed.