Effects of carbon segregation and interface roughness on the mobility of solid-liquid interface in Fe-C alloy: A molecular dynamics study

The kinetic coefficients (mu) for the fcc Fe-(0-0.5 wt%)C alloy solidification and melting were investigated using molecular dynamics simulations. The activation energy for the diffusion of C atoms (Q(C)) at the solid-liquid interface was calculated using the Debye-Waller factor to reveal the effect of C atoms dragging on the interface mobility. The influence of C segregation and interface roughness on interface mobility was also investigated. Simulation results show that for melting, the C content has a minor effect on the mu, and the mu is mainly ranged 18.1-19.4 cm/s.K, while for solidification, the mu linearly decreases with the increasing C content, and the mu is ranged 9.6-17.9 cm/s.K. In addition, a 'platform' zone was observed under low undercooling, in which the interface velocity is close to zero and suggests weak interface mobility, resulting from the segregation and dragging of C atoms at the interface. The `platform' zone size linearly increases with the increasing C content. The Q(C) increases with the increasing C content, which is ranged 0.71-0.91 eV for the fcc Fe-(0.1-0.4 wt%)C alloy solidification, indicating the C atomic motion is weakened and the C atoms dragging is reinforced due to C content increasing. Interface roughness and C atoms distribution analyses show that for the fcc Fe-C alloy solidification, a smooth solid-liquid interface is unfavorable for interface mobility, and the smooth interface is usually accompanied by the non-uniform distribution of C atoms. Therefore, increasing the interface roughness may be helpful for improving interface mobility and segregation for alloy solidification.

Automated summary

The kinetic coefficients for the fcc Fe-(0-0.5 wt%)C alloy solidification and melting were investigated. It was found that the mu decreases linearly with increasing C content during solidification, while C content has a minor effect on mu during melting. A 'platform' zone was observed under low undercooling, indicating weak interface mobility due to C segregation and dragging of C atoms.