Spatial correlation behavior between hydride and low-energy twin boundaries in Zr-4

Hydrogen embrittlement is an inevitable scientific problem of zirconium cladding materials in service or accident conditions, since the hydride precipitation deteriorates the mechanical properties, and damages the structure integrity. Twin boundaries (TBs) are the common low-energy defects inside the grain, whereas their spatial correlation with hydrides has been controversial to now. Here, we combined the first principle calculation and multi-scale characterization to reveal that the low-energy TBs can act as the preferred precipitation site of hydride in Zr-4. Compared with common intergranular hydrides, TB hydrides maintain the orientation relationship with the adjacent α-Zr matrix and twin. These findings can guide grain boundary engineering strategies for optimizing the resistance to crack initiation in zirconium alloy.