Interfacial characteristics and in situ nanoindentation analysis of hot-roll-bonded 316L stainless steel/Q370qE bridge steel clad plate

This study reveals novel interfacial mechanisms governing the metallurgical bonding and mechanical behavior of hot-roll-bonded 316L stainless steel/Q370qE bridge steel clad plates. EBSD analysis uncovers a distinct 15 μm transition zone with severe plastic deformation gradients: Q370qE exhibits deformed ferrite with abundant LAGBs, while 316L shows elongated austenite grains transitioning to fine-grained austenite near the interface. TEM identifies α′-martensite laths at the interface adhering to Kurdjumov–Sachs orientation relationships, alongside nanoscale Cr/Mo carbides precipitated through strain-assisted nucleation. Elemental diffusion analysis demonstrates a broad Cr transition zone contrasting sharply with Ni’s localized diffusion due to limited α-Fe solubility. Nanoindentation quantifies abrupt mechanical transitions, revealing a 48% hardness drop at the interface corresponding to Q370qE’s decarburized layer. Fracture morphology and in situ DIC confirm superior interfacial integrity with uniform strain distribution and dimpled fractures on both sides. These findings establish microstructure-property relationships critical for high-load corrosion-resistant applications.Graphical abstract