Computer simulations, for example by Ghaly and Averback (1994), had shown that a surface could produce a significant increase in the number of vacancy defects produced by displacement cascades in pure metals. In the present work, the influence of a surface on the production of lattice defects by displacement cascades of 10keV in the ordered alloy Ni3Al was studied. This alloy system was of interest because previous simulations, for example by Gao and Bacon (1995), showed that antisite defects, rather than Frenkel pairs, were the dominant defect species arising from cascades in the bulk. It was found that, for the near-surface cascades, the predominant defects were again the antisite atoms and their production in a disordered zone was enhanced by about 41% due to the surface. The production efficiency for vacancies was also much higher in the near-surface events and most of the extra atoms were created as adatoms on the surface. The surface resulted in a strong increase in vacancy clustering, to the extent that vacancy dislocation loops could be produced in the disordered zone by cascade collapse at low cascade-energy levels. The formation mechanism of a vacancy loop was investigated in detail.

The Influence of a Surface on Defect Production by 10keV Displacement Cascades in Ni3Al. Gao, F., Bacon, D.J.: Radiation Effects and Defects in Solids, 1997, 141[1-4], 395-407