KINETICS OF SHORT-RANGE AND LONG-RANGE B2 ORDERING IN TERNARY ALLOYS

The kinetics of disorder --> B2 order transformations in ternary alloys were studied in the pair approximation. The predictions of two sets of rate equations were compared, one based on an atom-atom interchange mechanism and the other based on an atom-vacancy interchange mechanism. Examples are presented to show how the evolution of order is affected by differences in interatomic potentials, differences in activation barrier heights, and effects of vacancy ordering. A wide variety of states of order are possible during the disorder --> order transformation in ternary alloys, and qualitative features of the sequences of these states are discussed. The sequences of states, or "kinetic paths", are much less intuitive than for binary alloys.