The effects of boron, cobalt or titanium additions upon the kinetics of order changes in Ni3Al under irradiation were investigated in a high-voltage electron microscope. The long-range order parameter was determined by measuring the intensities of superlattice spots on the diffraction patterns. Order-variation kinetics was investigated by using a previously proposed theoretical model. The number of replacements per displacement ε and the steady-state long-range order parameter S∞ were directly deduced by fitting a kinetic law to experimental data. Good agreement was generally found. A weak effect of the above third elements upon the disordering efficiency was observed whereas the effect of stoichiometry appeared to be more important. Re-ordering was found to be controlled by long-range vacancy migration with a migration enthalpy of 0.9 to 1.0eV; as deduced from a comparison of the experimental temperature dependence of the steady-state long-range order parameter with calculated curves. The effects of third elements upon the re-ordering kinetics were clearly revealed. Compared to binary alloys, a decrease of the effective re-ordering rate was generally observed.

The Effects of Third Elements on the Kinetics of Order Change in Ni3Al under HVEM Irradiation. Njah, N., Kolsi, A.W.: Annales de Chimie - Science des Materiaux, 1999, 24[2], 145-56