Disordering kinetics in Ni4Mo under irradiation with electrons and Mo ions

Disordering kinetics of Ni-Mo alloys in a Ni,Mo single-phase state with the D1(a)-type long-range ordered structure and two-phase state with Ni,Mo precipitates in an fee disordered matrix, was investigated under irradiation with 1 MeV electrons or 300 and 600 keV Mo ions. The change in degree of order was quantitatively evaluated from intensity attenuation of superlattice reflections recorded on imaging plates. The Ni,Mo phase was completely disordered with 1 MeV electron irradiation at 300 K, while the disordering proceeds only partially at temperatures higher than 373 K. Irradiation with 300 or 600 keV Mo ions caused the complete disordering state at 300 and 573 K where the disordering rate was almost equal to that under electron irradiation at 300 K. The difference in the disordering processes between electron and Mo+ ion irradiation is discussed in terms of the effects of displacement cascades.