A multi-scale study on the effect of interfacial microstructure on interfacial strength and fracture behaviour in Fe/Ni bonded interfaces

S Liu and S Nambu, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, 884, 145567 (2023).

DOI: 10.1016/j.msea.2023.145567

Multilayered Steel (MLS) enables impressive strength-ductility combinations by controlling the interfaces. Previous studies indicated that the interface is affected by various factors at multiple length scales, whereas their mechanisms had not been fully clarified. In this study, we focused on the effects of interfacial microstructure on interfacial strength of Fe/Ni interface. At macro scale, the pre-exist grain boundaries (GBs) were controlled to fabricate bicrystal and polycrystal interfaces. Uniaxial tensile test results showed that the bicrystal interfaces exhibit relatively higher interfacial crack initiation strength compared to the polycrystal interfaces. In-situ observation revealed that the decreased strength was owing to the unique crack initiation mechanism: the pre-exist GB-interface junctions behaved as weak spots in tensile separation. At atomic scale, interfacial atomic behaviour at the junctions was investigated by the molecular dynamics (MD) simulation method. The result indicated that the disordered High- Angle GBs (HAGBs) blocked the growth of interfacial dislocations and formed local dislocation pile-ups, where subsequent crack initiation was observed. This is attributed to the relatively lower intrinsic bonding strength at the GB-interface junctions.

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