Hydride-induced degradation of zirconium alloys: a criterion for complete ductile-to-brittle transition and its dependence on microstructure

Hydride-induced embrittlement is an important problem in hydride-forming materials. In this paper, a model is built for analysing a hydride-induced degradation process of the mechanical properties of zirconium alloys. A time-dependent criterion is proposed for determining the critical conditions of complete ductile-to-brittle transition. The dependence of this criterion on microstructure of Zr alloys is analysed in detail. The results show that many factors simultaneously govern the hydride-induced degradation. These factors include the susceptibility of hydrides to rupture, hydride size, hydride distribution, active slip systems, zirconium grain orientation, grain–boundary structure, grain–boundary density, hydrogen concentration, applied stress state and temperature. Intergranular hydrides have a more important influence on the loss in ductility than intragranular ones. The results obtained in this paper are of particular interest for zirconium alloys used in nuclear application.