Synergistic deformation and fracture behavior of heterostructure Cu/1010 steel bimetal laminated composites

In plastic deformation of bimetal laminated composites (BLCs), strength variation, deformation behavior and ductile fracture are quite different from those in single material. The Cu/1010 steel BLCs with different thickness ratio were designed and prepared by continuous solid/liquid bonding. The yield strength (YS), plastic instability strain (PIS) and fracture mechanism were studied by tensile test, mathematical calculations and microstructure characterization. The rule of mixtures (ROM) and long-wavelength approach (LWA) were adopted to study synergistic deformation and the influence factor of PIS combined with the results of finite element method. The deformation behavior and fracture mechanism of the BLCs were analyzed by digital image correlation (DIC) and scanning electron microscopy (SEM). These results demonstrated that, the thickness ratio has a great impact on mechanical behavior of Cu/1010 steel BLCs. In addition to act as a slip barrier to prevent the expansion of the shear band, the interface also increases the YS and flow stress of the BLCs due to its unique strengthening effect. The plastic deformation of Cu/1010 steel BLCs changes from "Cu-dominated" to "1010 steel-dominated" as the volume fraction of Cu decreases, resulting in the decrease in PIS from 25.2% to 12.2%. The PIS calculated by adding accumulated damage to the original LWA was closer to the experimental results, and the maximum error is reduced to about 0.1. The transition of failure mechanism is significantly affected by the strain-hardening and microdefects of the two layers. The current results link the accumulation of microscopic damage to the macroscopic plastic instability, and are of great significance to the understanding of the tensile deformation behavior and fracture mechanism of BLCs.