The Ordering of Ni₃V

Stoichiometric Ni 3 V undergoes a cubic → tetragonal ordering transition (Al → DO 22 ) by means of nucleation and growth. Electron diffraction microscopy and other experimental techniques reveal that the reaction is continuous, proceedind in three stages: I. Nucleation of coherent particles of the ordered phase in clusters of common orientation; II. Growth of these clustered nuclei to impingement forming isolated cells of unique orientation ‐ each cell is subdivided into anti‐phase domains; III. Growth of the cells to consume the remaining disordered phase, producing a mosaic substructure of mutually orthogonal cells, or “transformation twins”. Severe internal strains develop during the sequence, and secondary structural changes, such as twinning and recrystallization, effect their relief.