Temperature-sensitive ductilization in hydrogen-alloyed Fe-Cr-Ni austenitic steel by enhanced deformation twinning

Abstract

Solute hydrogen (H) is recently identified to improve the strength and ductility of some Fe-Cr-Ni austenitic steels due to a combination of solid-solution hardening and accelerated deformation twinning. In the present study, the impact of deformation temperature (173∼373 K) on this ductilization effect was studied primarily under a slow strain rate in Fe-24Cr-19Ni steel pre-charged with 7570 at ppm H. Ambient temperature was found to be an optimized condition where H-induced ductilization was the most pronounced. With the lowering temperature below 200 K, ductilization was mitigated entirely in spite of still substantial H-induced twinning enhancement. The result was ascribed to an overly prompted twinning activity and its premature density saturation, encompassing a consummation of work-hardenability at an earlier deformation stage.