Microstructure of ion-irradiated stoichiometric NiAl intermetallic: a comparative image simulation and transmission electron microscopy study

A comparative image simulation and transmission electron microscopy (TEM) study has been addressed in order to assess whether NiAl intermetallic undergoes a crystalline-to-amorphous transformation directly induced by the cascade. For this purpose, an NiAl single-crystal specimen has been irradiated with 6 MeV nickel ions to 0.1 dpa (maximum) and observed by conventional TEM in weak-beam imaging mode. This work shows that a crystalline-to-amorphous transformation directly induced by the cascade does not occur (absence of amorphous halo). Image simulation reported a defect cluster size of 2.8 nm as compared to a mean value of 3.0 nm measured on the experimental micrograph. The same image simulation study reported a defect cluster density of 1.7 x 10(24) m(-3) whereas a direct measurement from the experimental micrograph indicates 1.4 x 10(23) m(-3), a value about 10 x lower, most probably due to the resolution limit of the technique and also due to the contrast transfer functiori oscillation along the specimen thickness, which might render a fraction of defect clusters invisible.