Improving ductility of multilayer TWIP/Maraging steel through shear band delocalization and periodic multiple necking controlled by layer thickness

Layer thickness is a crucial parameter for enhancing the strengthening-toughening effects of multilayer steels. In this work, the tensile behaviors of multilayer TWIP/Maraging steels reveal a notable size effect dependent on layer thickness. The fracture elongation and work hardening gradually increase with the decrease of layer thickness, which is attributed to the gradual increase of micro shear bands and periodic multiple necking during the tensile deformation. These intertwined phenomena effectively dissipate the deleterious impacts of localized strains and promote strain delocalization. The multilayer with a thinner layer possesses enhanced tensile strength, mainly attributed to the refined elongated grains. The observed phenomena, along with the corresponding evolution processes of the shear band and periodic necking, are also simulated using finite element analysis based on local disturbance theory. This work further clarifies the effect of layer thickness on the synergistic deformation behavior and the toughening mechanism of heterogeneous multilayer steel.