Estimation of Fracture Toughness for ε Zirconium Hydride by Vickers Microhardness Indentation Method

Zirconium based alloys, as refractory metallic materials, can be fabricated into brittle zirconium hydride by hydrogen charging and can then be used as neutron moderators in the nuclear industry. In this study, the fracture toughness of bulk ε zirconium hydride was attempted to be estimated by means of Vickers microhardness indentation. Several representative semi-empirical formulas based on Palmqvist and half-penny crack models were adopted, and relevant parameters including Young’s modulus, Vickers hardness, indentation dimension, and crack length were respectively determined. It was observed that cracks began to nucleate at impression corners and peripheries when the load was higher than 500 gf. Crack length at 1000 gf was measured and used to estimate the fracture toughness. The results showed similar values to previous reports obtained from conventional experimental means, indicating that Vickers microhardness indentation is an available method for estimating the fracture toughness of ε zirconium hydride.