The B2 and DO₃ Ordering Reactions in Iron–Silicon Alloys in the Vicinity of the Curie Temperature

The ordering reactions in iron–silicon alloys have been studied by transmission electron microscopy in the composition range 10–17 at.-%Si and the temperature range 535–822°C. It has been found that: The A2 → B2 ordering reaction appears to occur homogeneously (i.e. in the non-classical manner) both above and below the Curie temperature, Te . The magnetic interaction suppresses the A2 → B2 critical temperature by about 100°C in Fe–10 at.-%Si. The B2 → DO3 ordering reaction appears to occur homogeneously above Tc , but by nucleation and growth below Tc . Antiphase boundaries nucleate phases with lower degrees of order than has the matrix but not phases with higher degrees of order. Long-range-order fluctuations occur near the critical points of the homogeneous A2 → B2 and B2 → DO3 transformations.