Directional disordering prior to amortization in electron-irradiated Cu-Ti intermetallic compounds

Abstract

At temperatures below approximately 265 K, intermetallic compounds in the Cu-Ti binary alloy system undergo an amorphizat ion transformation when irradiated by high energy electrons. Previous in-situ experimental studies revealed that the irradiation first induces chemical disordering in the compound (seen as a reduction in superlattice reflection intensity) which is followed by the crystalline-amorphous (C-A) transition. However, the actual structural evolution of the material during the C-A transition was not addressed in the previous study.In the present study, the structural evolution of the compound Cu4Ti3 was studied by ex-situ diffraction experiments in irradiated material that had not received a sufficient electron dose for amorphization. Cu4Ti3 has a Frank-Kasper-type tetragonal crystal structure composed of seven stacked body-centeredtetragonal sublattices.In Fig. 1, a diffraction pattern of the (017) systematic reflections is shown prior to complete amorphization. The double arrows mark the location of intersections of the first-order amorphous halo with the second-order halo arising from the (017) reflections and the Ewald sphere.