Zn interlayer modulates Al/Mg FSW reaction pathways: Mg-Zn phases suppress brittle intermetallic compounds

B Song and S Ma and ZX Zhu and YY Ling, WELDING IN THE WORLD (2025).

DOI: 10.1007/s40194-025-02222-z

The interfacial reaction control between Al and Mg alloys during friction stir welding (FSW) presents a fundamental challenge in solid- state joining technology. This work develops an innovative Zn-interlayer approach to address the persistent issue of brittle Al-Mg intermetallic compounds (IMCs) formation. Molecular dynamics (MD) simulations elucidate the preferential diffusion behavior of Zn in the Mg matrix compared to Al, establishing the thermodynamic basis for interfacial design. Advanced microstructural characterization via scanning electron microscopy (SEM) with energy-dispersive X-ray photoelectron spectrometer (XPS) reveals the dual role of the Zn interlayer as: a diffusion barrier that physically separates Al/Mg atomic interactions; a reactive element forming beneficial Mg-Zn phases instead of detrimental Al-Mg IMCs. X-ray diffraction (XRD) analysis confirms the absence of Al12Mg17/Al3Mg2 phases. The synergistic effects lead to a remarkable improvement in joint integrity without observable Al-Zn intermetallics formation. This study provides new insights into interface engineering for dissimilar alloy systems through intermediate layer design.

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