Nanoindentation studies of high-temperature oxidized Zircaloy-4 with and without hydrogen

The nanoindentation tests on high-temperature oxidized fuel claddings with/without hydrogenation were performed in order to verify the influence of hydrogen on mechanical behavior of the cladding under a loss of coolant accident (LOCA) condition. Hydrogenated and non-hydrogenated Zircaloy-4 cladding tubes were oxidized in steam at the temperature of 1373-1393 K followed by quenching. The nanoindentation test was performed in the area of inhomogeneous structure called as the Widmann-Statten structure, composed of the needle-like a-zirconium grains (alpha' phase) and the matrix (alpha phase). The mechanical properties viz. hardness and elastic modulus were evaluated for a' phase and matrix alpha phase, separately. The hardness and elastic modulus of alpha' phase are much higher than those of the matrix alpha phase due to its higher oxygen concentration. There was no significant difference of mechanical properties between the samples with and without hydrogen. (C) 2007 Elsevier B.V. All rights reserved.