Determination of Free Energy of δ-Ferrite/γ-Austenite Interphase Boundary of Low Carbon Steels by In-situ Observation
Phase transformations of δ-ferrite/γ-austenite in low carbon steels containing 0.017 mass% phosphorus are observed <I>in-situ</I> by using a combination of confocal scanning laser microscope with infrared image furnace. Dihedral angles at triple points of one high energy δ/δ grain boundary and two incoherent δ/γ interphase boundaries are measured by holding the sample at temperatures where δ- and γ-phases co-exist in quasi-equilibrium. From the average value of observed dihedral angles, free energy of γ/δ incoherent boundary for a steel with low sulfur content (0.007 mass%) is estimated to be 0.450 J/m<sup>2</sup> at <I>ca.</I> 1700 K. The effects of temperature and sulfur content on the dihedral angle and free energy of incoherent δ/γ boundary are also discussed.
- ISIJ international
ISIJ international 38(8), 794-801, 1998-08-15
The Iron and Steel Institute of Japan