Formation of Point Defect Clusters in Metals with Grain Boundaries under Irradiation

Molecular dynamics simulations have been performed to investigate the defect structure evolution at different development stages of atomic displacement cascades with energies up to 50 keV in iron crystallites in the temperature range from 300 to 900 K. The number of surviving radiation defects in iron crystallites increases according to a power law with increasing energy of the primary knocked-on atom. An increase in the crystallite temperature slightly increases the number of surviving defects. It is found that atomic displacement cascades can lead to radiation-induced grain boundary migration due to the melting and crystallization of the radiation-damaged region. The crystallographic orientation of the irradiated free surface strongly affects the radiation damage behavior. Craters with adatom islands are formed on the (111) free surface, and vacancy loops are nucleated in the (110) near-surface region. Point defects aggregate into clusters of various types during the evolution of atomic displacement cascades. It is shown that the number of surviving point defect clusters can significantly decrease under uniaxial elastic compression.