4. Tensile Deformation Behavior of Al-rich Ferritic Steels for Advanced Light Water Reactors

Following the Fukushima Daiichi incident, there has been considerable interest in developing accident-tolerant fuel cladding materials to make light water reactors (LWRs) more resistant to such accidents. Traditionally, zirconium-based alloys are used as the fuel cladding material in these reactors. Exothermic reaction with steam under accident conditions may lead to production of hydrogen with the possibility of catastrophic consequences. Hence, aluminum-rich (around 5 wt%) ferritic steels such as FeCralloy, APMT^TM and APM^TM have potential for accident-tolerant fuel cladding applications. These materials create an aluminum-based oxide scale protecting the alloy at elevated temperatures. Tensile deformation behavior of FeCralloy and APMT^TM alloy was compared at different temperatures (25–500 °C) and strain rates, and correlated with microstructural characteristics. Serrations appeared in the stress–strain curves of these alloys tested in a limited temperature range (300–400 °C). Presence of serrations did not lead to a decrease in elongation to fracture despite showing negative strain rate sensitivity behavior. The appearance of serrations is explained on the basis of dynamic strain aging (DSA) effect due to solute–dislocation interactions.