LONG-RANGE ORDER KINETICS IN NI3AL0.4FE0.6

Isothermal relaxations of the electrical resistance of Ni 3Al0.4Fe0.6 resulting from the long-range order (LRO) evolution were measured between 743 and 833 K, i.e. within the L1 2-ordered gamma '-phase domain. Both ordering and disordering kinetics were measured. The LRO relaxations were generally much faster than in the previously studied Ni3Al. The experimental curves fitted single exponentials; however, the Arrhenius plot of the resulting relaxation times yielded different values of the activation energy below and above 800 K, which is a Curie point of the alloy. Moreover, the estimated activation energies of long-range ordering and disordering within the ferromagnetic phase differed from each other. The results were discussed in terms of the magnetic order effect on atomic ordering and of the model of vacancy diffusion in L12 structures proposed by Schoijet and Girifalco.