Hydrogen-enhanced orientation dependence of stress relaxation and strain-aging in Hadfield steel single crystals

The effects of electrochemical hydrogen charging on the stress relaxation and strain-aging of 〈111〉- and 〈001〉-oriented single crystals of Hadfield steel were studied under tension at room temperature. An orientation dependence of stress relaxation and strain-aging-assisted yield-drop phenomena was observed for hydrogen-free 〈111〉- and 〈001〉- oriented single crystals. Hydrogen charging up to five hours increased the stress relaxation rate for slip-associated deformation in 〈001〉-oriented single crystals and decreased it for twinning-assisted deformation in 〈111〉-oriented specimens. The present results demonstrate that different mechanisms dominate the interaction of hydrogen with dislocations, stacking faults and twins.