Alloys of the Fe-Cr system: the relations between phase transitions “order-disorder” and “ordering-separation”

Using transmission electron microscopy and X-ray diffraction, a detailed study of the phase transformations in the Fe-Cr system in the alloys Fe-30; 40 and 47 wt.% Cr has been conducted. Since the phase transformation “ordering-separation” occurs on a level of changes in the electronic structure, it can be assigned as a phase transition of the second kind. It takes place in the Fe-Cr system at 900 ± 50 °C and 560 ± 10 °C. The temperature, at which the phase transformations “order-disorder” take place including “separation-solid solution” and “ordering-solid solution”, have been refined. An improved version of the Fe-rich portion of the Fe-Cr phase diagram is presented.