Hydrogen-induced ductilization in a novel austenitic lightweight TWIP steel

This study reported a novel hydrogen-induced ductilization in an austenitic lightweight twinning-induced plasticity (TWIP) steel (Fe-1C-25Mn-5.5Al-3Si, in wt. %). This phenomenon was irrelevant to strain rate or global work hardening rate. In fact, the stacking fault energy (SFE), 49.5 mJm−2, of the steel is an appropriate value for hydrogen-induced ductilization. This SFE was reduced by hydrogen and deformation twin was enhanced in the hydrogen-rich surface layer during deformation. Such twinning-strengthened surface limits formation of strain localization and allows extra deformation. Besides, this SFE is high enough so that martensitic transformation and hydrogen-enhanced intergranular cracking were absent, making the steel free from hydrogen embrittlement. This work provides a new concept that SFE/twinability engineering not only prevents hydrogen embrittlement but enables hydrogen-induced ductilization. [Display omitted]