Hydrogen embrittlement of titanium sheet under multiaxial states of stress

The influence of hydrogen on the ductility of commercially pure titanium sheet has been investigated over a range of stress states from uniaxial to equibiaxial tension. The data show that hydrogen embrittlement of plastically anisotropic Ti sheet depends on stress state, being the most severe in equibiaxial tension. Quantitative metallography indicates that the effect of stress state is primarily a result of two factors: (1) plane strain and equibiaxial tensile deformation are especially effective in causing the strain-induced fracture of hydrides and consequently void formation, and (2) the void link-up process in plane strain and equibiaxial tension initiates at a comparatively low bulk void density. The results are analyzed in terms of the influence of stress state on both hydride fracture and the occurrence of shear instabilities triggered by hydride fracture/void nucleation. © 1984