The effect of hydrogen on the deformation behavior of zirconium alloys at elevated temperatures

Hydrogen ingress inevitably happens in zirconium alloy parts during the operation of nuclear reactors: resultantly hydrides form at low temperatures as brittle phases that can significantly reduce the alloys’ ductility and fracture toughness. Interestingly, upon the increase of testing temperature to above 200ºC, there is a brittle to ductile transition for hydride containing zirconium alloys. Possible mechanisms that might control the transition to ductile deformation might be associated with plasticity in both zirconium and/or hydrides, and enhanced plasticity in zirconium due to solute hydrogen atoms (hydrogen enabled softening). This proposal utilizes in-situ uniaxial tensile tests during diffraction at elevated temperatures on zirconium samples with and without hydrogen, so that the effect of solute hydrogen atoms on the activation of different slip systems can be studied through the analysis of lattice strain evolution. The generated strain data will be complemented by in-situ SEM HRDIC tests that reveal strain localization on individual grains. The goal is to understand whether solute hydrogen atoms can induce deformation behavior change of zirconium, and the magnitude of softening if there is, and providing deeper understanding of the brittle-ductile transition behavior.