Fe-Fe3C binary phase diagram in high magnetic fields

The Fe-Fe3C binary phase diagram under high magnetic fields up to 21 T was investigated by a differential thermal analysis. Applying a magnetic field of 18 T, the α-γ transformation temperature Tα-γ for pure iron increased quadratically from 1181 K (a zero field) to 1206 K. With increasing magnetic field strength, the transformation temperature Ac1 (α-Fe + cementite → α-Fe + γ-Fe) increased linearly from ∼1000 K to ∼1030 K at the rate of 1.4-1.5 K T−1. The transformation temperature Ac3 (α-Fe + γ-Fe → γ-Fe) for Fe-0.18 wt.%C and Fe-0.38 wt.%C increased quadratically by 27 K under a 18-T field. The Ac1 and Ac3 lines shifted to higher temperatures by the magnetic field, resulting in a change in the Fe-Fe3C phase diagram. The results obtained suggest that the transformation temperatures mainly arose because of the Zeeman energy of α-Fe under high magnetic fields.