Phase-field modelling of the thermo-mechanical properties of carbon steels

The high temperature stress model for continuously cast steels has been developed. The effect of dendritic morphology on the mechanical strength of carbon steels has been investigated for the first time with a thermodynamically based calculation of dendritic morphology by a phase-field model. The characteristic solid fraction at the liquid impenetrable temperature (LIT) was evaluated as 0.9 by investigating the contact behavior of secondary arms during unidirectional solidification of δ and γ phases. Geometrical hardening of the mushy zone due to the contact and combining of dendrite arms has been evaluated using a geometrical hardening parameter defined as the contact ratio between adjacent secondary arms in the transverse cross section of primary arms. The critical solid fraction at zero strength temperature (ZST) was evaluated as 0.65 from the minimum non-zero contact ratio. The calculated critical fracture strength with the stress model for steels in a mushy zone describes the measured tensile strength well.