Study on Hydrogen-Induce Ductility Loss in YB70 Steel

Hydrogen-induce ductility loss in YB70 steel was investigated by measurements of tensile properties as well as TEM and SEM analyses of deformation and fracture.The result shows that the hydrogen-induce ductility loss in YB70 steel exceeds 80% when tensile specimens were hydrogen-charged for more than 2 h.Some transgranular cracking along slip planes can be observed on the tensile fracture surface of specimens hydrogen-charged.Hydrogen segregation near the interface between the matrix and carbide precipitates promotes the dislocation movement in tensile deformation,leading to a high density of tangled dislocations to be located at approximately 15 nm from the interface.The cracking is formed at the position with the high density of tangled dislocations and propagated along slip planes,which results in the ductility loss of YB70 steel.