Effects of (α+β) heat treatment on the hydrogen embrittlement of zircaloy-4

The influence of the characteristics of (α+β) heat-treated Zircaloy-4 on the hydrogen embrittlement was investigated. The hydride morphology was related to the microstructural characteristics produced by the (α+β) heat treatment. Mechanical properties were discussed with the hydride morphology and the characteristics produced by the (α+β) heat treatment. The hydride was large with the length of about 50∼150 μm and precipitated more or less parallel to the rolling - transverse plane along grain boundaries. The residual stresses produced during water quenching affected the hydride morphology more than other factors such as microstructure and texture since the hydrides precipitated mainly along grain boundaries and the changes in crystallographic texture produce the low variation of volume fraction of basal poles 0-30· from reference direction, VR with increasing volume fraction of the transformed β, fα,. Total elongation decreased markedly after the hydrogen charging due to the preferred precipitation of large hydride along grain boundaries and triaxial stress state in necked region after UTS. But the UTS and uniform elongation were not varied between the hydrogen uncharged and charged specimens, irrespectively of fα, because hydride may experience some plastic deformation