Molecular dynamics investigation on crack-healing and tensile deformation mechanisms in zirconium under overlapping collision cascades

Abstract

In this work, molecular dynamics simulations were performed to investigate the interaction between the micro-crack and overlapping collision cascades in zirconium. A comprehensive analysis of the formation and recombination of irradiation defects was conducted to gain an atomic-level understanding of crack healing. Crack healing occurs when the thermal spike’s core covers the crack due to the recrystallization of atoms with high kinetic energy after the first collision cascade. We delved into the formation mechanism of vacancy dislocation loops in crack-healing Zr under overlapping collision cascades, which account for the combined effects of overlapping collision-induced vacancy collapse and recrystallization-induced vacancy migration. The uniaxial tensile deformation of crack-free and cracked Zr was extensively studied before and after irradiation. Strength enhancement was observed after crack healing, inhibiting pyramidal slipping and promoting the formation of nanotwins during the tensile process. The movement of nanotwin planes controls dislocation nucleation and movement.