Enhancing strength-ductility synergy of multilayer metals by periodic necking: Experiments and simulations

Abstract

Multilayer metals are typical heterostructured materials where superior strength-ductility synergy is sought by combining materials with significant mismatches in mechanical properties. Strain delocalization has been identified as a pivotal mechanism for improving their ductility. However, the strategy for achieving this enhancement through manipulating the critical geometrical and mechanical factors pertaining to multilayer materials remains unclear. In this study, the uniaxial tensile behavior of multilayer TWIP/maraging steels is investigated through experiments, which unveil periodic necking-assisted plasticity regulated by the properties of constituent materials, rendering the multilayer steel both strong and ductile (Ultimate strength∼1.5 GPa, fracture straiñ15%). To explore optimized strategies for enhancing this advantage, detailed finite element simulations are performed on the tensile deformation of multilayer TWIP/maraging steels with varying geometrical and mechanical parameters. The formation of periodic necks observed in experiments is successfully reproduced by employing a ductile damage model for the constituent material and a cohesive zone model for the interface. Comprehensive simulation results revealed that within the parameter range studied in this work, the layer thickness ratio is the most relevant factor dominating the strength-ductility synergy, while the layer thickness, interface strength, interface thickness, and strain hardening ability of the TWIP steel mainly affect the ductility rather than strength. This research contributes to our understanding of ductility mediated by strain delocalization and provides valuable insights for the design of multilayer metals.