Effect of microstructure factors and cold work on the hydride precipitation in zircaloy-4 sheet.

Abstract

The effects of microstructure factors and manufacturing process on the precipitation of hydrides in Zircaloy-4 plate have been studied. A quantitative technique described in Ref. 1 has been used to evaluate the susceptibility to radial hydride formation under the influence of texture, residual stress and externally applied tensile stress. Image treatment was carried out to determine the average orientation of hydrides. The hydride oriented threshold stresses were estimated, following an improved approach which had been firstly developed by Sauthoff and then applied to Zr-H system by Puls.2 Both analytical and experimental results indicate that the threshold stress is influenced by the microstructure and thermomechanical treatment of Zircaloy-4, and by the hydrogen concentration in a very complex manner. After examining the hydride morphologies of formerly cold-rolled sheets of two different fabrication routes in stress-relieved, recrystallized and β treated states, it may be concluded that the distribution morphology of hydrides can be selected, and their noxiousness and effective contribution to the embrittlement can be thus minimized by controlling texture, grain structure, and manufacturing process.