| Abstrakt: |
Evolution taking place under irradiation of cascade region (CR) in copper during the thermal spike has been simulated by molecular dynamics technique. It is shown that over time intervals of ∼10-12 s in CR with sufficiently big sizes there is a possibility of quasimelting, during which the majority of atoms change their initial positions. The defect structure of the cascade region does not qualitatively change immediately after crystallization. However, at T≃0.7-0.8 Tm vacancies, because of the temperature gradients, move preferentially towards the centre of CR. It is shown that at "fast" cooling (∼6 1014 K/s) they form finally a depleted zone with higher (∼2 times) concentration of vacancies as compared to the initial one; and at "slow" cooling (∼2 1014 K/s) they form a void of irregular form, which at lower temperatures (∼0.7-0.4 Tm can transform, because of the thermal pressure in CR, into the Frank dislocation loop over the period of ∼10-10 s. An analysis has been made of the experimental data indicating the possibility of "slow" cooling in metals located in the middle of the periodic system and of "fast" cooling-in metals located at the end of it. |
