Cyclic deformation and microstructural evolution of 316L stainless steel with pre-charged hydrogen

This study investigates the cyclic plastic deformation and microstructural evolution of hydrogen-charged 316L stainless steel. The results of low-cycle fatigue tests indicate that the samples with and without pre-charged hydrogen exhibit initial cyclic hardening and sequential cyclic softening at a low strain amplitude (≤0.5 %). However, a secondary cyclic hardening at a high strain amplitude (≥0.7 %) is observed near the end stage in both uncharged and hydrogen-charged samples. Microstructural evolutions characterized by electron backscattered diffraction and scanning transmission electron microscopy reveal the evident hydrogen-assisted dislocation nucleation and motion, which significantly enhances the accumulation of dislocation in the first cyclic hardening stage, resulting in fewer cycles to reach the first peak of responding stress amplitude. Moreover, the observed hydrogen-assisted twinning accelerates the formation of the secondary peak of stress amplitude. The hydrogen-assisted dislocation and twinning evolutions contribute to a reduction in the fatigue life of the steel.