Effects of hydrogen on the mechanical response of α-uranium

The presence of hydrogen is known to embrittle and drastically reduce the ductility of α-uranium. However, it has not been established whether aging amounts of hydrogen alter the mechanisms of plastic deformation (i.e. slip and twinning). In-situ neutron diffraction experiments and polycrystalline plasticity modeling were employed to address this issue. Samples were thermally charged to 0.3 and 1.8 wppm H then tested in-situ. It was seen that hydrogen charging decreased the ductility drastically. However, it did not affect the bulk plastic deformation processes. Specifically, the grain-level onset of dislocation glide and deformation twinning as well as the hardening behaviors of the individual mechanisms remained consistent between samples. The texture evolution did not change with hydrogen content either. What did clearly change with increasing hydrogen content was the fracture mechanism, which transitioned from transgranular ductile rupture to brittle intergranular decohesion.