Ordering processes and activation energy in Ni3Fe-based ternary alloys

Abstract

The measurement of electrical resistance (ϱ) has been used, to study the kinetics of isothermal ordering in the range 200 °–545 ° C in Ni3(FeMn) alloy quenched from 970 ° C, and the kinetics of ordering at 390 ° C in the alloy quenched from various temperatures in the 600 °–800 ° C range. The sections method and the gradient of the ϱ(t) curves were used to find the activation energy for migration and vacancy formation in this alloy on the assumption that the excess vacancies “frozen” in the alloy by quenching at temperatures above Tc are responsible for ordering. The activation energies for vacancy formation and migration were respectively ΔU0 = 33 ± 3 kilocal/mole and ΔUm = 39 ± 4 kilocal/mole, which in total give the activation energy for diffusion Q = 72 ± 7 kilocal/mole in the alloy studied; this approximates to the activation energy for diffusion in pure nickel.