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. (C) 2017 Acta Materialia Inc Published by Elsevier Ltd. All rights reserved.