Melting of thin γFe-C films having (100), (110) and (111) surfaces in terms of molecular dynamics simulation

Structural changes associated with melting of thin γFe-C films having (100), (110) and (111) surfaces have been investigated by molecular dynamics simulation. Structures of thin film and bulk models of γFe containing about 0-4 at.% C were calculated at constant temperatures between 1000 and 1800 K. The liquidus temperature for each thin film model decreased with increasing the C concentration. Comparison between the atomic number density distributions of Fe and C showed: (i) The atomic number density of C near the surface increases before the formation of liquid near the surface, (ii) This increase becomes more prominent as temperature rises, (iii) Melting of γFe-C alloy would be rate-controlled by diffusion of C from the solid phase to the solid-liquid interface. These findings suggest that the increase in the C concentration enhances atomic vibrations of Fe near the surface and promotes melting of Fe at lower temperatures. Furthermore, it has been concluded from Lindemann's law of melting that surface melting occurs in γFe-C alloy having (110) surface more easily.