Steady-state creep of zircaloy-4 fuel cladding from 940 to 1873 K

Abstract

Steady-state creep rates of as-received zircaloy-4 fuel cladding have been determined from 940 to 1073 K in the α-Zr range, from 1140 to 1190 K in the mixed (α + β) phase region and from 1273 to 1873 K in the β-Zr phase region. Strain rates of between 10 −6 and 10 −2/s were determined under constant uniaxial load conditions. Assuming that creep rates can be described by a power law-Arrhenius equation, the creep rate for α-phase zircaloy-4 is given by: ge ss ̇ = 2000 σ 5.32 exp(−284 600/kT) s −1 ; for the β-phase zircaloy-4 by: ge ss ̇ = 8.1 σ 3.79 exp(−142 300/kT) s −1 ; and for the mixed (α + β) phase of zircaloy-4 (for creep rates ⩽3 × 10 −3 s −1) by: ge ss ̇ = 6.8 × 10 −3 σ 1.8 exp(−56 600/kT) s −1 . For the both the α and β phases, the activation energies for creep are in agreement with those of self-diffusion. For the mixed (α + β) phase region, the low creep rate range is controlled by grain boundary sliding at the α/(α + β) phase boundary.