The Fe-Feinf3/infC 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 Tinfα-γ/inf for pure iron increased quadratically from 1181 K (a zero field) to 1206 K. With increasing magnetic field strength, the transformation temperature Ainfc1/inf (α-Fe + cementite → α-Fe + γ-Fe) increased linearly from ∼1000 K to ∼1030 K at the rate of 1.4-1.5 K Tsup-1/sup. The transformation temperature Ainfc3/inf (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 Ainfc1/inf and Ainfc3/inf lines shifted to higher temperatures by the magnetic field, resulting in a change in the Fe-Feinf3/infC phase diagram. The results obtained suggest that the transformation temperatures mainly arose because of the Zeeman energy of α-Fe under high magnetic fields.
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