Ion induced disordering and dissolution of Ni3Al precipitates

The disordering of homogeneous Ni3Al and decomposed Ni(Al) alloys under irr adiation with 300 keV Ni-58 ions is studied at room temperature. In order t o determine the development of the long-range order parameter, electron dif fraction patterns are quantitatively evaluated taking into account dynamica l diffraction effects. Although postulated by a recent model based on the t hermal spike concept, no finite rest order is observed in the high-dose lim it. The disordering rate of Ni3Al precipitates is much higher than that of homogeneous Ni3Al which is explained by the additionalchemical dissolution of the particles due to ballistic mixing. (C) 1998 American Institute of Ph ysics. [S0003-6951(98)01949-4].