In situ resistometric investigation of ordering kinetics in Ni3Al

The kinetics of atomic long-range order (LRO) in the intermetallic compound Ni3Al has been studied in situ by means of high temperature resistometry. The isothermal relaxation of the resistivity has been measured after restoring the equilibrium state of the sample at 1173 K and quasi-quenching down to 862, 880, 925 and 973 K. The experimental LRO relaxations in Ni3Al fitted first-order kinetic curves reasonably; however, while an exponential decrease of the resistivity was registered both at 862 and 880 K, an increase was observed at 925 and 973 K. The effect has been discussed within the model proposed by Rossiter (1979, 1980). The activation energy of the process was found to be approximately 3 eV which was in agreement with the previous data of diffusion and with the sum of vacancy formation and migration energies recently evaluated in Ni3Al.