Fe-rich portion of the Fe-Cr phase diagram: electron microscopy study

Transmission electron microscopy and the corresponding selected-area electron diffraction patterns of Fe-(10;20;30;40;47) wt. pct. Cr alloys heat treated isothermally from 500°C up to 1500°C at 100°C was employed to construct the equilibrium Fe-rich portion of the Fe-Cr phase diagram. It has been found to be quite different from the generally accepted one. Two regions of phase separation are in the diagram at low and high temperatures. Two lines of the second-order phase transition “ordering-separation” are pointed also. The σ-phase region in the diagram is considered as a region containing two phases, namely, the σ-phase surface layer and the solid solution bulk.