Strong resistance to hydrogen embrittlement via surface shielding in multi-layered austenite/martensite steel sheets

Abstract

Layered architectures have been applied to twinning-induced plasticity (TWIP) steel in terms of configuring multi-layered TWIP and martensitic steel (MLS) sheets to overcome the limitation of low yield strength. However, hydrogen embrittlement (HE) inevitably appears in materials used for high-strength purposes, with the interfacial layers presenting localization sites of hydrogen, thereby limiting the materials' broad structural applications. Here, we present a novel design for MLS sheets that exhibit both strong resistance to HE and a good strength-ductility balance via surface shielding. Our hydrogen penetration data demonstrates that the proposed austenitic shielding structure effectively acts as a barrier to hydrogen due to the reduced hydrogen diffusivity, compared with existing MLS sheets. We propose the optimal surface thickness required to play the role of shielding layer based on the quantified diffusivity and the rule of mixtures of the layer fractions, which presents a plausible novel design for layered architectures that exhibit strong resistance to HE and possess tunable mechanical properties.