The isothermal relaxation of long-range order after small temperature changes was investigated in Ni3Al intermetallic compounds (with 24.6, 25.0 and 26.5at%Al) by measurements of the residual electrical resistivity. The equilibrium residual electrical resistivities were found to be consistent with theoretically calculated values of the long-range order parameter. The approach to equilibrium could be satisfactorily represented by a sum of two exponentials; the relaxation rate was minimum at the stoichiometric composition. The activation enthalpies of the two processes were not significantly different (2.63 to 2.88eV); they do not display an important composition dependence. A model was proposed for explaining the existence of the two isothermal relaxation processes.

Kinetics of Long-Range Order Relaxation in Ni3Al: the Effect of Stoichiometry. Dimitrov, C., Zhang, X., Dimitrov, O.: Acta Materialia, 1996, 44[4], 1691-9