The evolution of defects in a material under irradiation is studied at low doses (∼5 dpa or less) using rate equations. It is shown that as a function of temperature at a critical valueTc a transition occurs in the behaviour of the solutions of the rate equations. BelowTc the voids show incubation effects. An expression is derived for the critical dislocation density at which the void growth starts. This is related to the trapped vacancy fraction ε in vacancy dislocation loops. AboveTc the incubation effects are shown to be related to the gas production rate which becomes the rate controlling parameter in determining the evolution of the defects. A gas-bubble to void transition occurs at a critical void radius and expressions are derived for the critical void size and dose at which the transition appears. It is shown that closely related to this is the incubation dose for interstitial loops. Finally, these features are corroborated by actual numerical integration of the rate equations.
Volume 96, 2022
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