Thermal creep behavior of precipitation-strengthened wrought FeCrAl cladding tube at different temperatures

FeCrAl alloys are recognized as an excellent candidate material for accident-tolerant fuel cladding tubes. However, thermal creep behaviors of FeCrAl alloy cladding tubes and the associated microstructural evolution have not been comprehensively investigated. This work addressed this gap by evaluating the axial thermal creep behavior of precipitation-strengthened wrought FeCrAl alloy cladding tubes at the temperatures of 360°C and 475°C, respectively. Creep test results indicated that there was a threshold stress for the FeCrAl alloy cladding tubes, because the thermal creep strain rate increased rapidly when the thermal creep stress was larger than a specific stress level. Consequently, a power-law thermal creep constitutive model with a threshold stress was established according to the thermal creep test results. Creep failure was primarily caused by shear stress. In addition, microstructural analysis indicated that the grain size of the FeCrAl alloy cladding tubes initially increased and subsequently decreased with increasing applied stress. Both the dislocation density and the proportion of low-angle grain boundaries demonstrated a decreasing trend with increasing stress levels.