RADIATION EFFECTS IN FCC METALS AND INTERMETALLIC COMPOUNDS - A MOLECULAR-DYNAMICS COMPUTER-SIMULATION STUDY

We review recent results on the mechanisms of atomic mixing, radiation-induced disordering, and defect production and clustering induced by displacement cascades in Cu, Ag, Cu3Au and Ni3Al. We employ molecular dynamics computer simulation (MD) methods with isotropic many body potentials and recoil energies near the subcascade formation regime (up to 30 keV). Atomic mixing is shown to be dominated by diffusion in the locally molten cascade core in both the pure metals and the intermetallic compounds. Disordering of the intermetallics was found to take place in the core of the cascades. However, because of the short lifetime of the displacement cascade, chemical short range order is preserved in the molten zone. Our results reveal the appearance of very large vacancy and interstitial type defect clusters at high recoil energy and cascade energy density. Vacancies agglomerate and collapse into Frank dislocation loops as the result of the quenching of the cascade molten core. Large interstitial clusters are directly produced in cascades and form prismatic dislocation loops. The fraction of defects in clusters for low temperature cascades increases with recoil energy and approaches approximate to 70% and 60% for interstitials and vacancies, respectively, at recoil energies near the threshold for subcascade formation. In the case of intermetallic (A(3)B) compounds, the large energy required to produce and transport a superdislocation appears to inhibit the interstitial prismatic loop punching process and interstitials appear as isolated (100) dumbbells formed by pairs of majority-type atoms.