The Prediction of Creep behaviors of Zircaloy-4 Using Uniaxial Stress Relaxation

Zirconium alloys have been used as a reactor component material because of their favorable neutronic properties, good mechanical behavior at elevated temperature and high corrosion resistance. In reactor operation condition, creep is one of the significant degradation mechanisms in zirconium alloys. Recently, creep is known as a critical factor which threatens the integrity of cladding with hydride reorientation in dry storage condition. However, the evaluation of creep is not easy, because creep test requires a considerable time. It is known that stress relaxation and creep are correlated analytically. Creep behavior can be derived from stress relaxation test with a relatively short time. In this paper, creep behavior of Zircaloy-4 is predicted using uniaxial stress relaxation. Creep behaviors of Zry-4 were predicted using stress relaxation. The stress relaxation test was conducted under tensile stresses of 65-187MPa at 400 .deg. C. The stress relaxation results were analytically converted to the predicted creep curves. The saturated primary creep strains (ε_sat) were 0.029 mm/mm at 100MPa and 0.033 mm/mm at 120 MPa. The steady state creep rates (ae_ss) were 2.48*10^-8s^-1 at 100 MPa and 2.22*10^-7s^-1 at 120 MPa. The predicted creep behavior for 100 MPa coincided well with the experimental data but that for 120 MPa was not