Microstructure and texture analysis of [delta]-hydride precipitation in Zircaloy-4 materials by electron microscopy and neutron diffraction

Abstract

This work presents a detailed microstructure and texture study of various hydrided Zircaloy-4 materials by neutron diffraction and microscopy. The results show that the precipitated [delta]-ZrH1.66 generally follows the [delta](111)//[alpha](0001) and [delta][1{\overline 1}0]//[alpha][11{\overline 2}0] orientation relationship with the [alpha]-Zr matrix. The [delta]-hydride displays a weak texture that is determined by the texture of the [alpha]-Zr matrix, and this dependence essentially originates from the observed orientation correlation between [alpha]-Zr and [delta]-hydride. Neutron diffraction line profile analysis and high-resolution transmission electron microscopy observations reveal a significant number of dislocations present in the [delta]-hydride, with an estimated average density one order of magnitude higher than that in the [alpha]-Zr matrix, which contributes to the accommodation of the substantial misfit strains associated with hydride precipitation in the [alpha]-Zr matrix. The present observations provide an insight into the behaviour of [delta]-hydride precipitation in zirconium alloys and may help with understanding the induced embrittling effect of hydrides.© 2014, International Union of Crystallography.