Experimental Evaluation of Interfacial Free Energy of Solid Iron

Interfacial free energy of solid iron was experimentally evaluated for solid/liquid interface and grain boundary of austenite phase in solid Fe/liquid FeO-SiO2 system. Multi-phase equilibrium method was adopted and two kinds of angles such as dihedral angle between solid/liquid interface and grain boundary, and contact angle of sessile drop of molten oxide on solid iron were measured. On the basis of experimental results and literature data of activity of FeO, surface tension of liquid FeO-SiO2 oxide and solid Fe, interfacial tension (interfacial free energy) of solid/liquid interface and grain boundary of gamma-Fe were evaluated. Oxygen partial pressure in the experimental atmosphere was evaluated as 1 x 10(-12)similar to-10(-11 )atm. Under this condition, solid/liquid interfacial free energy was evaluated as 1 440-1 500 mJ/m(2) and grain boundary free energy of gamma-Fe as 860-940 mJ/m(2) at 1 350 degrees C. The evaluated value for the grain boundary was agreed well with the data of previous works.