XXXI. On the migration of atoms in iron-nickel alloys

Abstract

A summary of the results obtained with alloys quenched from temperatures between 500° C. and 800° C. is contained at the end of Section 2 of the paper. Measurements were made to determine the lattice parameters of the constituents of alloys in the two-phase region. The alloys were subjected to different heat treatments after annealing at 500° C., 400° C., and 350° C. respectively. The curves showing the relation between composition and parameter of both α and γ-components are of different shapes according to the manner in which the heat treatments are carried out. On the interpretation of these curves suggested in the paper, it is possible to so vary the heat treatment as to make nickel atoms to migrate either from the α-to the γ-structure or from the γ-to the α-structure, and the measurements enable this migration of atoms to be studied in some detail for an annealing temperature of 500° C. Useful information in this connexion is also supplied by the alloys annealed at 400° C. and 350° C. The results point to the formation of nuclei of α-phase alloy which are small enough in the initial stages to cause particle scattering of the incident radiation, but this component of the two-phase alloy appears to be in a stage of equilibrium corresponding to the temperature of annealing. The α-phase, on the other hand, either does not reach its final state of equilibrium during the heat treatments to which the alloys were subjected, or it exists in the form of nuclei which are even smaller thau the e-nuclei. The investigation is of a preliminary nature.