Characterization of dynamic recrystallization phenomena in newly designed advanced austenitic stainless steels for developing liquid hydrogen storage technology

This paper presents the dynamic recrystallization (DRX) behaviour of three newly designed austenitic stainless steel (ASS) compositions (designated as SS, SS-Mn, and SS-Nb) to develop and produce advanced high-strength materials for liquid hydrogen (LH 2 ) storage systems through thermomechanical processing. While Alloy SS is essentially 304 L with 0.09 wt% N, SS-Nb is its microalloyed variant with 0.1 wt% Nb and reduced N content (0.035 wt%). Alloy SS-Mn is based on 201LN grade with reduced Ni (5.4 wt%) content and alloyed with high Mn (7 wt%) and N (0.2 wt%) contents. To establish the characteristics of dynamic softening, uniaxial single-hit hot compression experiments were conducted using Gleeble 3800 thermomechanical simulator at 950–1200 °C, 0.001–0.1 s −1 . Hot compression stress–strain analysis using the Poliak–Jonas criterion and EBSD reveals discontinuous DRX (DDRX) as the dominant mechanism in low SFE ASSs under varying temperatures and strain rates. Rising temperature and strain rate promote conversion of low- to high-angle grain boundaries, increasing twins and DRX, with SS and SS-Nb showing earlier DRX despite Nb drag, while SS-Mn exhibits higher stresses and slower DDRX due to solid-solution strengthening, sluggish boundary migration, and residual δ-ferrite in SS/SS-Nb aids recrystallization pathways, highlighting how composition and processing govern ASS microstructures.