Conditions of existence of a disordered solid solution having chemical interactions between the atomic species

Conditions of existence of a disordered solid solution, in which the tendencies toward phase separation or ordering take place, are analyzed. The formation of separation microstructures in the solid solution region of a Fe-Cr phase diagram is discussed. It is shown that the tendency toward phase separation takes place in the region which is called now as the solid solution region. It is noted that a chemical phase transition termed “ordering-separation” occurs on going from the region of ordering to the one of phase separation.