Creep constitutive model for FeCrAl alloy cladding tube: experiments and molecular dynamics simulations

FeCrAl alloy serves as a promising accident-tolerant fuel cladding material for nuclear reactors. The structural integrity of nuclear fuel throughout the reactor’s service life critically depends on the cladding's creep behavior. Researchers have proposed several constitutive models to predict the high-temperature creep response of FeCrAl alloy tubes. However, the development of reasonable and reliable constitutive models necessitates extensive experimental validation due to the complex interdependencies governing creep behavior. This study aims to establish a new creep constitutive model for FeCrAl alloys through molecular dynamics (MD) simulations and experimental validation. Constitutive model parameters were fitted based on the MD simulation results of high-temperature creep of FeCrAl alloy under a wide range of grain size, temperature, and stress conditions. Subsequently, the key parameters were optimized against the material's bulk mechanical properties and biaxial creep test data. The developed constitutive model was implemented in finite element analysis (FEA) to simulate biaxial creep behavior of thin-walled FeCrAl tubes. A good quantitative agreement was observed between the FEA predictions and the measured results for both axial and hoop creep strain rates. Furthermore, the model is validated against uniaxial creep data from open literature, confirming its reliability in simulating both biaxial and uniaxial creep behavior of FeCrAl cladding tubes. The proposed model can achieve at least an order of magnitude improvement in prediction accuracy over the ORNL (Oak Ridge National Laboratory) model.