Development of a Heterogeneous Lamellar Structure Based on Layer Instabilities during Accumulative Roll Bonding

The strategy of designing heterogeneous structures has emerged as a new tool in avoiding the prominent strength-ductility trade-off dilemma in metallic materials. However, methods to reproducibly synthesize heterostructured materials with effective microstructural control are still elusive. Herein, a highly reproducible method based on conventional accumulative roll bonding (ARB) and postannealing is proposed for designing heterostructured Cu samples with precisely defined heterogeneous lamellar structure (HLS) wherein the size, volume fraction, and spatial distribution of coarse and fine grains can be accurately controlled. An optimal heterogeneous lamellar microstructure is found which gives rise to a roughly 3 times higher yield strength than that of coarse-grained Cu and a good tensile ductility of & AP;34.7% total elongation. Experimental observations reveal that the unique HLS induces strong heterodeformation-induced hardening and promotes dislocation accumulation, leading to the observed exceptional strength-ductility synergy. This novel fabrication method is applicable to a considerably larger number of metal systems and can be utilized to further tailor HLS to optimize the mechanical properties of metals.