Study of hydrogen-induced delayed fracture in high-Mn TWIP/TRIP steels during in situ electrochemical hydrogen-charging: Role of microstructure and strain rate in crack initiation and propagation

Abstract

The initiation and propagation of hydrogen-induced cracks (HICs) in high-Mn twinning/transformation-induced plasticity (TWIP/TRIP) steels were explored by slow strain rate tension test. For TWIP/TRIP steels with 10% phase volume fractions of ε-martensite (PVFM), the initiation of HICs is dominated by dislocation slips at 1 × 10−6 s−1, but, at 1 × 10−5 s−1, it is dominated by deformation twins. For TWIP/TRIP steels with 45% PVFM, inconsistent deformation of ε-martensite promotes HICs initiation. Both Σ3 grain boundary and γ/ε phase interface with Nishiyama-Wassermann orientation could prevents HICs propagation. And ε-martensite with <0001>||RD microscopic orientation at the crack tip is more likely to induce transgranular crack propagation.