Chemical interactions between dissimilar atoms exist always, in all alloys and at any temperature.

Many alloys have the ability to change the sign of the chemical interaction energy with temperature.

Change of the sign of the chemical interaction energy changes the type of microstructure.

Ordering-phase separation’ transitions in the Co₂V alloy occur at 800 and 450 °C.

Methods of determining temperature of the transition ‘ordering-phase separation’ are proposed.