“Order–Order” Kinetics In Ni50.5Al49.5 single crystal by quasi-residual resistometry

Kinetics of “order–order” reactions in B2-ordered Ni50.5Al49.5 intermetallic was examined by means of quasi-residual resistometry. Isothermal relaxations of quasi-residual electrical resistance of the sample, measured in liquid nitrogen bath, were associated with corresponding relaxations of the concentration of antisite defects, proportional to the long-range order parameter. rly as in the case of previous “in situ” experiments, the observed relaxations were very sluggish with relatively low activation energies: E A ( o r d )  = (2.37 ± 0.10) eV for ordering and E A ( d i s )  = (1.93 ± 0.19) eV for disordering process. These energies are lower than the activation energy for Ni self-diffusion in NiAl (3.0 eV), but somewhat higher than the one previously determined by means of “in situ” resistometry for “order–order” processes in Ni50.5Al49.5. The origin of low relaxation rates observed in the experiment has recently been elucidated by atomistic Kinetic Monte Carlo (KMC) simulations in terms of low disordering efficiency of atomic jumps in triple-defect B2-ordering binary systems.