Temperature effects on defect production and disordering by displacement cascades in Ni3Al

Molecular dynamics simulations are used to obtain detailed information on defect production and disordering produced in the primary cascade state of radiation damage in Ni3Al as a function of irradiation temperature Tirr, Although the number of Frenkel pairs decreases with increasing Tirr, the size of interstitial clusters and the interstitial clustering fraction increase with temperature. Temperature has a strong effect in enhancing the production of antisite defects, for the number per cascade increases by about 20% as Tirr increases from 100 K to 600 K, and then by about 90% as it increases further to 900 K. These effects are believed to be due to the increase in the intensity and lifetime of the thermal spike. The average size of disordered zones at different temperatures in the simulations is compared with experimental transmission electron microscopy data and the results are in reasonable agreement. The long range order parameter in the cascade region is found to be consistent with values obtained experimentally on Ni3Al irradiated by ions to a similar damage dose. The chemical short range order parameter is about 0.6 over the whole range of T irr considered, suggesting that the cascade core retains some short range order at high temperature due to local reordering.