Influence of stress field of expanding and contracting plate shaped precipitate on hydride embrittlement of Zr-alloys

The stress fields of expanding (precipitation) and contracting (dissolution) hydride plates were computed by finite element method using Zr–H solid solution and hydride properties at 25, 200 and 400 °C for fully and semi-constrained hydride plates. For the first time simultaneous hydride expansion and matrix contraction and vice-versa have been considered in a simulation of hydride precipitation and dissolution, respectively. It was observed that a fully constrained expanding hydride plate exerts a tensile stress field in the matrix close to the edge of the hydride plate while a partially contracting hydride plate exerts a tensile stress field in the hydride plate as well as a large compressive stress in the surrounding matrix close to the edge of the hydride plate. It is suggested that a compressive stress component in the matrix acting normal to a partially shrinking hydride plate could possibly explain an enhanced resistance to hydride embrittlement of Zr-alloy at elevated temperature.