Quantifying hydrogen concentration in the vicinity of zirconium hydrides and deformation twins

Abstract

This study focuses on investigating the effects of the localized stresses that develop during formation of zirconium hydrides on the redistribution of hydrogen atoms in the zirconium matrix. A coupled mass diffusion and crystal plasticity finite element approach is used. The effects of the transformation strain associated with the formation of hydrides within various combinations of soft-hard grains and tri-crystals are studied. In addition, the interaction between intergranular and intragranular hydrides with grain boundaries is investigated. It is shown that hydrogen atoms tend to diffuse towards the tips of hydrides and away from their sides due to the tensile and compressive hydrostatic stresses that respectively develop at these two locations. This results in the propagation of a hydride along its axial direction. It is further shown that under a tensile applied stress, hydrides tend to form and propagate within hard grains, where stress hotspots with high tensile hydrostatic stresses develop. Lastly, it is shown that hydrogen atoms tend to diffuse towards twin tips, particularly when the twin tip is located near a harder grain.