Developing a dual-mode confined layer slip model for Al/Mg composites with incoherent FCC/HCP interfaces: Insights from molecular dynamics studies

The classic Hall-Petch model effectively captures the relationship between strength and layer thickness for thicknesses above 100 nm, while the constrained layer slip (CLS) model provides a better prediction for thicknesses below 100 nm. Nonetheless, the precision of the current CLS model is insufficient, especially for structures with FCC/HCP interfaces, which limits the development of lightweight composites such as Al/Mg. To address this gap, this study uses molecular dynamics (MD) simulations to explore the CLS mechanism under compression in Al/Mg composites. We propose a novel dual-mode CLS model aimed at enhancing the accuracy of stress predictions across a wide range of layer thicknesses and various slip angles. Our findings indicate that with decreasing layer thickness and the loss of lattice structure, the FCC/HCP interface becomes unstable and exhibits reduced strength when the layer thickness falls below 26.7 nm. Moreover, as the slip angle rises from 0° to 75°, the improved interface compatibility aids in the initiation of basal slip in the Mg layer. This triggers a migration of dislocations from the Al side to the Mg side, thereby altering the dominant CLS mechanism. This work is expected to accelerate the development of Al/Mg composites and other similar FCC/HCP composite systems.