Experimental study and molecular dynamics simulation of 2A12 aluminum alloy diffusion bonded joint with Ag interlayer

As a widely used high-strength aluminum alloy in aerospace, 2A12 faces challenges in conventional fusion welding due to its susceptibility to hot cracking. Diffusion bonding has emerged as a promising technique to achieve good joints while preserving mechanical properties. Molecular dynamics (MD) simulations and vacuum diffusion experiments were employed to study the diffusion behavior of Ag interlayers in 2A12 aluminum alloy bonding. An MD model for the Ag(111)/Al(111) interface was developed. At 793 K, Al atoms exhibited a significantly higher diffusion coefficient toward Ag (0.47 Å²/ps) than Ag toward Al (0.003 Å²/ps), demonstrating their dominant role in the diffusion process. The interfacial microstructure of the vacuum-brazed joint was examined using EPMA and SEM. Results indicated that intermediate phases preferentially formed on the Ag side. The bonded interface exhibited a continuous distribution of Al₂Ag intermetallic compounds interspersed with Ag₂Al phases. The combined MD simulation and experimental results demonstrated that Al atoms primarily contribute to surface diffusion at the interface, whereas Ag atoms facilitate long-range penetration through grain boundary diffusion. Under the parameters obtained from experiments (783 K, 5 MPa, and 60 min), the diffusion bonded joint achieved a maximum shear strength of 111.7 MPa. It promotes the formation of metallurgical bonding layers and inhibits brittle Ag₂Al phase coarsening. The present study innovatively realizes the theoretical–experimental validation of the diffusion behaviors across the scales and offers a theoretical foundation for the optimization of the diffusion joining process of aluminum alloys.