Order-disorder transformations and lattice defects were studied by performing positron lifetime measurements. Anomalous vacancy generation, during ordering transformations, was confirmed. Disordered face-centered cubic solid-solution Ni3Fe was brought to room temperature by quenching the specimen from temperatures above the order-disorder transformation point. The ordering process in the L12 structure was promoted by heating isochronally or isothermally. It was found that vacancies were generated during both heating processes. The vacancies generated were not stable up to the order-disorder transformation point, and annealed out at temperatures below that point.

Excess Vacancies Induced by Disorder-Order Phase Transformation in Ni3Fe. P.Chalermkarnnon, H.Araki, Y.Shirai: Materials Transactions, 2002, 43[7], 1486-8