Cascade overlap induced amorphization and disordering in irradiated intermetallics NiAl and Ni3Al: A molecular dynamic study

The kinetics of amorphization and disordering processes in NiAl and Ni3Al induced by collision cascades have been investigated by means of molecular dynamic (MD) computer simulations, It has been shown previously (Spaczer el at. [Phys. Rev. B 52, 7171 (1995)]), that the interaction between the electron and the phonon systems of the lattice, which is simulated by removing the kinetic energy through a coupling factor, plays a key role on the evolution of the cascade. In the ordered NiAl, a 15 keV cascade leads to the formation of an amorphous region, while in the ordered Ni3Al and for the same conditions no evidence of amorphization could be observed. In NiAl the amorphized region was the largest when an intermediate coupling parameter (so called weak coupling) was employed. In the present paper we report MD simulations of collision cascades created in partially disordered lattices. This partial disordering results from a previous 15 keV PKA cascade using weak electron-phonon coupling parameter. Both the influence of the initial chemical disordering on the cascade and the fate of the amorphous clusters are investigated. We observed that the amorphous cluster is preserved and grows in the cases of the weak and no coupling in NiAl while for strong coupling conditions the final microstructure is crystalline and highly disordered.