Orientation of hydrides in zirconium alloy tubes

The effects of crystallographic texture, grain size and shape, and tensile stress on the orientation of hydride platelets in Zircaloy-2, Zr-2.5Nb, and Excel tubes have been studied using transverse ring and longitudinal tension specimens. When the α grains are equiaxed, the hydride platelets precipitate either at grain boundaries or on the basal plane. A sufficiently high tensile stress perpendicular to the basal plane will precipitate the platelets perpendicular to the stress. When the grains are thin and elongated, the platelets precipitate along the grain boundaries. When the basal plane normals are close to a longitudinal axis of the grains, a sufficiently high stress will precipitate the platelets perpendicular to the stress and the platelets will cut across the grain boundaries