Effect of external stress on hydride reorientation in zirconium

The usage and long-term storage of nuclear fuel cladding motivate efforts to understand the effect of external stress on hydride precipitation. Here, by using in situ bending device in electrolytic hydrogen charging, the nucleation and precipitation behaviors of subsurface hydrides under different degrees of tensile stress were obtained. The number density of surface hydride bumps increases with the elastic tensile stress and reaches a peak before plastic yielding. This is related to the statistical result that the reorientation of hydride bumps reaches maximum at the end of elastic stage. Morphologies of hydride bumps varies from needle- or circular-shape to faceted, indicating hydride reorientation. The faceted hydrides have special crystallographic characteristics. Under tensile stress, the habit planes of faceted hydrides gradually transform from {0001} to {10 1 ¯ i} ( i = 1–7), even to the {10 1 ¯ 0} planes. Because of the local compressive stress, faceted hydrides growing along one <11 2 ¯ 0> direction are suppressed. External stress-stimulated tensile or compressive lattice stress on specific crystallographic planes impacts the choice of faceted/habit planes in hydride precipitation, which plays an important role in the long-term performance of Zr cladding tubes.