Mitigating hydride embrittlement in zirconium via twin-twin networks

Brittle hydride precipitation and fracture are primary causes of hydrogen embrittlement in zirconium (Zr). Mitigating hydride-induced cracking through microstructural design remains a challenge. Here, we demonstrate that twin boundaries (TBs) can be manipulated to effectively curb hydride precipitation and thwart hydride-induced ductility loss. Microscopic analysis reveals that TBs act as preferential nucleation sites for hydrides, with parallel long twins promoting continuous nucleation and growth of hydrides along TBs and in turn facilitating hydride-induced cracking. In contrast, a high density of intersecting narrow twins limits hydride growth and packing, yielding fine-sized hydrides that exhibit enhanced room-temperature deformability. These finer hydrides are likely to also serve as effective sources for pyramidal <c+a> dislocations, which helps to further suppress hydride-embrittlement and enhance ductility. The TB/hydride relationship discovered here introduces a potential pathway for designing hydride-embrittlement resistant microstructures. © 2026 Acta Materialia Inc.