Unique fracture behavior and strengthening mechanism of SUS304/45 multilayer steel with network structure

A new type of SUS304/45 multilayer steel with network structure was designed and fabricated by warm rolling and quenching. The soft SUS304 layers with coarse grains are fragmented into island-chain networks (island fragments refer to the fragmented structure formed by the fracture of the soft phase SUS304 layer after warm rolling, dispersed in the matrix of hard phase 45 steel, constituting the 'island chain' of the network structure.) embedded within the fine-grained hard phase 45 steel matrix. The tensile strength and fracture elongation of 600 °C rolled + quenched (W600-Q) multilayer are 1600 MPa and 14.7 %, respectively, which are significantly higher than those of 1000 °C rolled + quenched (W1000-Q) multilayer. High temperatures alleviate stress concentration near the shear zone, facilitating dislocations slip along the shear direction and promoting their movement and proliferation. The improved properties are attributed to heterogeneous deformation-induced (HDI) stress and the activation of multiple micro shear bands (SBs) in the network structure of the W600-Q sample, which displays distinct ductile shear fracture characteristics. This study provides an experimental foundation and theoretical guidance for developing metallic structural materials with excellent strength-toughness synergy.