HYDROGEN-INDUCED CRACKING OF COMMERCIAL PURITY TITANIUM

Slow straining of compact tension specimens of commercial-purity titan ium has been employed for assessing the likelihood of failure due to h ydrogen pick-up in titanium containers For nuclear fuel waste disposal . Results indicate that slow crack growth occurs by a ductile tearing process at low hydrogen concentrations. No fast crack growth occurs at such hydrogen levels, apparently because ductile collapse relaxes the stresses and prevents the attainment of a sufficiently high stress in tensity for fast crack initiation. Fast propagation of a brittle crack was observed only at hydrogen concentrations above a critical value t hat depended upon the material involved and the orientation of the cra ck relative to the manufactured microstructure. An empirical relations hip suggests that the higher the strength of the titanium involved the lower is the critical hydrogen level for brittle failure. Both the di stribution of residual beta-phase and the texture of the fabricated ma terial influence the susceptibility of a particular specimen orientati on to fast fracture. Published by Elsevier Science Ltd.