Abstract
Research on Cr-coated Zircaloy (Zry) as the most near-term solution for Accident-Tolerant-Fuel (ATF) concept has been boosted in the last decade, while a great concern is addressed on the interfacial failure between coating and substrate. In this study, Cr-Zry bilayer plates were firstly prepared using the diffusion bonding method at different temperatures (1073 and 1273K), subsequently the tensile tests were performed at RT and 573K. The finite element method (FEM) was further applied to simulate the stress distribution and evolution in the Cr-Zry specimen during the tensile test by ABAQUS. The results show that the Cr-Zry bilayer specimens exhibit distinctly different deformation behaviors between RT and 573 K: a two-stage deformation is noted for RT test and no sudden mechanical response for 573 K test, which is attributed to the ductile-to-brittle-transition of Cr. Besides, the fractography reveals delamination and cracks near the Cr/Zry interface at 1273 K-bonded specimens, indicating weak bonding with a higher presence of ZrCr2. Cracks initiating at the interface propagate to the two layers when plastic deformation occurs, caused by the local stress concentration and the followed prefracture at the interface. The presence of interlaminar shear stress is confirmed by FEM simulation, which is due to the transverse stress difference between Cr and Zry layers in the vicinity of the interface, which is probably responsible for the delamination of the Cr-layer. The obtained insights from this study indicate that the Cr-Zircaloy-4 interface is a weak point for Cr-Zry system materials, which will be essential to understand the mechanical behavior of Cr-coated Zr-based ATF claddings in reactors.
