Evaluation of mechanical properties of irradiated zirconium alloys in the vicinity of the metal-oxide interface

The mechanical properties of oxides play an important role on the protection of underlying metals from further oxidation. Such properties should be examined to provide further mechanistic understanding of oxidation phenomena. This paper presents a novel method for determining the mechanical properties of material at the two sides of the metal-oxide (M/O) interface. It is applied to Zircaloy-2 cladding from a boiling water reactor. Two samples irradiated for 3 and 9 years have been examined. Micropillars were fabricated in the vicinity of M/O interface in the oxide, metal, and transition region using focused ion beam (FIB). The pillars were then uniaxially compressed using nano-indentation. Results prove the ability to pinpoint and consistently measure Young's modulus and yield strength of specific regions around the M/O interface. The Young's modulus and yield strength of metal and oxide regions for the two Zircaloy-2 samples are reported.