Simulation of defect cascade collapse in hcp zirconium

Using the molecular dynamics method, the mechanism of vacancy loop (VL) nucleation in depleted zones (DZ) of displacement cascades in hcp zirconium has been investigated in terms of the thermal spike model. It is shown that the type of nucleation VL (basal or prism) depends on the average volume concentration of vacancies C v ∗ in the depleted zone at the moment of its crystallization at the thermal stage of development of the displacement cascade. At the vacancy concentration C v ∗ = 10 at% in DZ of hep zirconium prism loops (101̄0) with Burger's vectors b = 1 2 〈10 1 ̄ 0〉 and b = 1 3 〈11 2 ̄ 0〉 predominantly nucleate. At C v ∗ = 15 at%, loops in the basal plane with b = 1 6 〈20 2 ̄ 3〉 were observed to nucleate. Simulation of various conditions of depleted zone cooling has revealed that in the case of accelerated DZ cooling conditions from the high-temperature region, formation of three-dimensional precipitate of the metastable bcc phase is possible.