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The effect of the pre-strain on hydrogen embrittlement (HE) of high strength steels was investigated by slow strain-rate tensile (SSRT). The specimens were electrochemically hydrogen-charged in 0.5 mol/L H 2 SO 4 with 1 g/L CH 4 N 2 S at room temperature for 24 h. It is found that the amount of hydrogen increases linearly with the exponent of pre-strain, i.e., C H = 11.963 + 0.00385 exp ( 1.144 ε P ) . The HE susceptibility of the alloy initially decreases and then increases with increasing pre-strain. The ultimate tensile strength for the hydrogen-charged specimen is highest in the 3% pre-strain, which is interpreted by competition between strain hardening and Hydrogen Enhanced Decohesion (HEDE) mechanism. The fracture mode shows a mixed mode fracture of quasi-cleavage and intergranular fracture for hydrogen-charged specimens while the fracture mode exhibits dimples for hydrogen-free specimens. [ABSTRACT FROM AUTHOR]

The present work investigated the effect of cathodic hydrogen-charging current density on mechanical properties of prestrained high strength steels. This was done by tensile tests on both hydrogen-charged and -uncharged prestrained specimens at a cross-head displacement speed of 0.03 mm/min. The influence of prestrain on hydrogen behavior was also studied using an electrochemical permeation technique. The results show that the relationship between ultimate tensile strength of the hydrogen-charged specimens (UTS-H) and prestrain depends on current density. The UTS-H decreases with increasing current density independent on prestrain. With an increase in prestrain the diffusion coefficient of hydrogen gradually decreases, which is attributed to increasing dislocations density acted as hydrogen traps. SEM fractograph reveals that hydrogen charging causes a change from ductile to brittle failure. [ABSTRACT FROM AUTHOR]