TEM INVESTIGATION OF NI4MO LRO AND SRO AFTER MEV ION IRRADIATION

100 MeV I9+ ions are irradiated to a fluence of 1X10(14) ions/cm(2) on 100 nm thin Ni4Mo long range ordered (LRO) and short range ordered (S RO) samples to study the effect of electronic energy loss in inducing order-disorder transformation. For this energy electronic energy loss is 2.9 keV/Angstrom. Transmission electron microscopic (TEM) investiga tions reveal dislocation loops and dislocation lines in the irradiated samples. Intensities of super-lattice reflections corresponding to SR O and LRO samples in selected area diffraction (SAD) patterns do not d ecrease appreciably after irradiation, indicating that the volume frac tion of the defects created is small. Careful analysis shows that in t he present system defect production due to electronic energy loss is n ot significant. This indicates that the threshold electronic stopping power required for damage production in Ni,Mo is greater than 2.9 keV/ Angstrom.