Understanding the hydride precipitation mechanism in HCP Zr polycrystals: a micromechanical approach

This study focuses on the hydride precipitation in zirconium polycrystals during thermo-mechanical cycles. The precipitation and dissolution of mesoscale hydrides in Zircaloy-4 is modelled using crystal plasticity finite element methods supported with DFT-informed zirconium lattice hydrogen concentration. Results for a tri-crystal case show the effects of crystallography, thermo-mechanical load and elasto-plastic anisotropy on hydride nucleation and growth. Analyses of polycrystalline models provide new insights into the complex precipitation process of hydrides in Zircaloy-4 with explicit representation of experimental observations that lay the foundation for further research in this field. Micromechanical findings demonstrate the importance of microstructure, pre-thermal condition, and hydrogen concentration limit on hydride precipitation. Overall, the study provides a deeper understanding of hydride formation during industrially relevant reactor conditions. Graphical abstract