Recoverable plastic strain in Zircaloy-2

Abstract

The relaxation of plastic strain in Zircaloy-2 is investigated. It is shown that the recoverable strain γ varies with time t _o according to the empirical relationship, γ = γ_o log(t/t _o). (1/t _o) is shown to increase with temperature γ_o is independent of temperature, but increases with prestrains up to ∼0.25 after which it remains constant. γ_o also varies from specimen to specimen in the batch investigated and this is attributed to impurity effects. The total recoverable strain is shown to be a constant fraction of the plastic prestrain up to γ ∼0.01 and has a constant value at higher strains. A dislocation model is developed to describe the total recoverable strain involving the runback of dislocation pile-ups.