Interface Shearing Promoted Plastic Flow Instability of Nanolaminated Composites

Abstract

Nanocrystalline laminated composites (NLCs) with alternating phases exhibit exceptional mechanical properties, thermal stability, and resistance to radiation damage and shock. However, inherent plastic flow instability poses a persistent challenge, independent of loading direction. This study explores the mechanisms of buckling and kinking in soft-hard and soft-soft NLCs under compression loading, attributing plastic deformation to dislocation slips and interface shearing/sliding. Despite these merits, plastic flow instability remains a challenge in NLCs under compression, irrespective of loading direction. This study focuses on elucidating the mechanisms of plastic flow instability, particularly buckling and kinking, observed in soft-hard and soft-soft NLCs. A mesoscale crystal plasticity model integrating the interfacial shear (IS) and confined layer slip (CLS) mechanisms is developed. In soft-soft Cu-Nb multilayers, the model reveals that easy interface sliding promotes plastic strain in the interface, inducing strain softening by lowering interface shear resistance. Conversely, the contribution of interface shear to plastic deformation diminishes with increasing Cu/Nb layer thickness, reducing the likelihood of strain softening. For soft-hard Al-Al2Cu eutectics, easier interface shear intensifies plastic deformation in Al layers but suppresses it in Al2Cu layers, triggering structural instability in the latter. The critical strain for bulking in the same thick Al2Cu layer decreases with increasing Al layer thickness. In summary, lowering interface resistance will promote compression instability of NLCs, while thickening soft layer will retard the occurrence of compression instability regardless of soft-soft or soft-hard NLCs.