Deformation-stored energy driven densification of yttrium hydride via hot-pressing sintering: Balancing full densification against high-temperature dehydrogenation

Yttrium hydride (YH x ) has attracted significant research attention in fields such as solid-state moderators for advanced nuclear energy systems, owing to its superior hydrogen storage density. However, traditional preparation processes struggle to overcome the intrinsic contradiction between the requirement for high densification and severe high-temperature dehydrogenation. Therefore, this study prepared YH x monoliths using a hot-pressing sintering process and systematically investigated the densification mechanism and micro-defect evolution under a strong thermo-mechanical coupling field. The results indicate that 750∼775 °C is the optimal sintering temperature window for balancing optimal processing window balancing near-full densification with controlled hydrogen retention. Its densification mechanism is fundamentally governed by the evolution of deformation-stored energy. In the initial stage of hot-pressing consolidation, the mechanical compaction dominated by external axial stress injects a high density of geometrically necessary dislocations (GNDs) and deformation stored energy into the matrix. As the temperature rises, ample thermal energy effectively activates the dynamic recovery and recrystallization processes of the matrix, releasing the lattice distortion energy through significant structural relaxation and large-scale dislocation annihilation. These findings provide an important reference for fabricating high-performance YH x components for advanced nuclear applications.