Control mechanism of Ni-foil on the interfacial structure and properties of the magnesium alumina laminated composite plate

The paper study the interfacial mechanical properties and structural evolution mechanisms in 6061/AZ31B/6061 composite plates with and without Ni foil interlayers. For Ni-free interfaces, a continuous diffusion layer (3.5–4.0 µm) forms, dominated by brittle columnar Al₁₂Mg₁₇ intermetallic compounds (IMCs, 0.27–0.35 µm thick), which act as preferential crack initiation sites. In contrast, Ni foil implantation induces interfacial restructuring during hot rolling: Constrained deformation fragments the Ni foil into grid-like segments with "olive"-shaped cross-sections, embedded into Mg/Al matrices. These fragments (56% areal coverage) coexist with dispersed multiphase IMCs (Mg₂Ni, Al₃Ni, Mg₃AlNi, Al₁₂Mg₁₇; 10–20 nm grains) at fragment edges, forming a hybrid interface of "willow-leaf" Al₁₂Mg₁₇ islands and nanoscale Mg₂Ni/Al₃Ni layers (15–25 nm). Hall-Petch analysis reveals the multiphase IMC interface exhibits 3.6 × higher "kd⁻¹/²" strengthening contribution than single-phase Al₁₂Mg₁₇ systems, attributed to grain refinement (20 nm vs. 260 nm average grain size). Synergistic effects of mechanical interlocking, adhesion hierarchy (Ni-Al > Ni-Mg >Al-Mg), and nanoscale reinforcement collectively enhance peel strength by 78% without compromising bulk tensile properties.