Molecular Dynamics Simulation: Comparative Investigation of Nanoscale CuAl2 and Fe Interlayers for Interfacial Strengthening–Toughening of Cu/Al Laminated Composites

The brittle nature of CuAl2 intermetallic layers severely limits the service reliability of Cu/Al clad materials in power electronics. Here, molecular dynamics simulations are performed to clarify the thickness-dependent deformation behavior of CuAl2 interlayers (0–40 Å) and to propose a ductile Fe interlayer modification scheme to overcome its intrinsic brittleness. Using identical model dimensions, EAM potentials, and loading conditions, the optimized 20 Å CuAl2 is set as the unified reference, and gradient Fe interlayers (10–50 Å) are quantitatively compared. The results reveal that CuAl2 exerts a non-monotonic regulation: the 20 Å interlayer achieves optimal strength–ductility synergy, while thicker layers (>20 Å) induce brittle cleavage. Substituting the 20 Å CuAl2 with an Fe interlayer of equal thickness improves peak tensile strength by 33.5% and suppresses the brittle-damage tendency under the present fully periodic simulation conditions. The 40 Å Fe interlayer exhibits the best comprehensive performance, delivering a 67.2% strength enhancement while maintaining comparable uniform plasticity. Crucially, unlike CuAl2 (effective only within 10–20 Å), Fe interlayers sustain favorable synergy across a broad 10–50 Å window. This superior performance originates from triple synergies: physical isolation buffering lattice mismatch, thickness-modulated slip transfer, and a fundamental shift in failure mode from cleavage to matrix-dominated plastic instability. Because periodicity constrains through-thickness crack propagation, this result represents a comparative trend under the specified simulation conditions rather than proof of crack immunity under free-surface conditions. This work provides atomic-scale guidance for interface design in high-performance Cu/Al laminates.