Zircaloy-4 sheet specimens oxidised in steam at 873K exhibited greater creep strain rates than non-oxidized Zircaloy-4 specimens when creep-tested in pure argon at 873K. This difference in the creep behaviors of oxidized and non-oxidized specimens is attributed to the existance of compressive stresses in the $ZrO_2$ layer and in the oxygen-rich α-phaselayer and counter-balancing residual tensile stress in the specimen core that arise from the large volume expansion of the oxide layer and the lattice dilatation of the α-phase layer.
Creep property data, elastic behavior of the oxide, the α-phase and the core, and the oxidation induced stress theory advanced by Donaldson and Evans were employed to compute compressive stresses and residual tensile stress, respectively. The residual tensile stress was calculated to be 3.7 to 37.6 MPa, being proportional to the scquare root of the oxidizing time. The compressive stress in the oxide layer was 490 Mpa and the compressive stress at the oxide/α-phase interface is 712 MPa. Then the oxidizing time did not significantly influence them. The oxide and the α-phase layer thickness increased proportionally to the scquare root of the oxidizing time when oxidized up to 100 hours. The above results are in reasonable agreement with other investigators.
