Interface strain gradient enabled high strength and hardening in laminated nanotwinned Cu

Interfaces play a crucial role in mechanical behaviors of laminated materials. In this study, a series of hard/soft nanotwinned Cu laminates with varying interface spacing from 200 to 33 μm are prepared by means of direct current electrodeposition. Simultaneous improvement of strength and work hardening with decreasing interface spacing is found in tensile tests. Extra strengthening and geometrically necessary dislocations (GNDs), but without any strain concentration, are found in the vicinity of interfaces. An obvious strain discrepancy appears across the interface and decreases with decreasing interface spacing. Most importantly, a highest plastic strain gradient appearing in the vicinity of interfaces, regardless of interface spacing, indicates a significant deformation compatibility across the interfaces. The spatially-distributed strengthening mediated by interface contributes for increasing strength and decreasing strain discrepancy by decreasing the interface spacing.