MD simulations of collision cascades in the vicinity of a screw dislocation in aluminium

Molecular dynamics has been applied to study the interaction of collision cascades with 1/2〈110〉 screw dislocations in aluminium. Primary knock-on atoms (PKA) with energy EPKA=5keV were initiated in Al crystals at temperatures ranging from 100 K to 600 K at different distances from the dislocation line. Capture of the displaced atoms from the collision cascade region by the dislocation core has been observed at all simulation temperatures and led to the formation of a helical dislocation segment. Apart from that, in the material subjected to external loading a displacement cascade in the vicinity of a screw dislocation can trigger dislocation cross-slip. Under applied stress the dislocation unpins from the helical segment with the formation of a mobile dislocation loop with 1/2〈110〉 Burgers vector. The number of residual vacancies and self-interstitial atoms produced in collision cascades near 1/2〈110〉 screw dislocations is evaluated and compared with the number of Frenkel pairs formed in collision cascades in the pristine material under the same irradiation conditions