Simulation of fracture behaviors in hydrogenated zirconium alloys using a crystal plasticity coupled phase-field fracture model

Abstract

Zirconium (Zr) alloys are widely used as fuel cladding materials in nuclear reactors; however, the formation of hydride precipitates within these alloys during service significantly reduces their ductility. The effects of hydrides on the fracture behavior of Zr alloys, particularly the role of misfit strain induced by hydride precipitation, remains inadequately understood. Additionally, there is a lack of robust mesoscale models to accurately describe the failure mechanisms of hydrogenated Zr alloys. In response, we develop a crystal plasticity coupled phase-field fracture model that accounts for the evolution of dislocation density, the degradation of critical energy release rate, and the coupling effects between plasticity and damage. The model is employed to investigate the effects of misfit strain induced by hydride precipitation, hydride orientation, and hydride volume fraction on the fracture behavior of hydrogenated Zr alloys. The study also explores the underlying microscopic fracture mechanisms in detail. The results demonstrate that the proposed model effectively captures the influences of hydrides on the ductility of Zr alloys. Specifically, an increase in hydride volume fraction leads to a significant reduction in the ductility and toughness of Zr alloys. The microscopic fracture characteristics of hydrogenated Zr alloys differ significantly between those containing circumferential and radial hydrides, resulting in substantially lower ductility and toughness in samples with radial hydrides under the same conditions. Most importantly, our simulations reveal that misfit strain induced by hydride precipitation is an indispensable factor leading to hydrogen embrittlement in Zr alloys. This research provides valuable insights into the failure mechanisms of hydrogenated Zr alloys and offers a powerful tool for accurately modeling their fracture behavior.