Hydrogen Embrittlement of a Prerolled High-Mn Steel with Different Cut-Edge Characteristics

Abstract

The hydrogen embrittlement behavior of a prerolled Fe–15Mn–0.65C–2Al–2Si high-Mn steel with various cut-edge properties is studied via hydrogen precharging and slow strain rate test. In the presence of hydrogen, samples prepared by laser cutting under atmosphere of N₂ exhibit the best total elongation at about 39%. Press blanking produces severe shear deformation, tensile residual stresses, and strain-induced martensite, resulting in a high risk to hydrogen-induced cracking. With compressive residual stresses produced from waterjet, corresponding samples exhibit the lowest elongation loss against hydrogen. Despite hydrogen charging, the fracture surfaces show transgranular quasi-cleavage features, for which mechanical twinning from prerolling plays a critical role. The hydrogen-enhanced decohesion mechanism accounts for cleavage fracture since hydrogen segregation reduces cohesive stress at twin boundaries.