Nanoscale analysis of interfacial structure and its effects on mechanical properties of Mg/Al laminate reinforced by TiB2 particles

Abstract

Fabricating Mg/Al laminate is an effective strategy to circumvent the inherently low formability and poor corrosion resistance of Mg alloys. Here, Mg/Al laminate with good bonding quality and mechanical properties was successfully fabricated via porthole die co-extrusion process using ZK60 Mg and TiB₂/6061Al composite as constituted layers. Integrating the results from microstructural characterization and mechanical testing, the effects of extrusion temperature on microstructure, interfacial structure, element diffusion, and mechanical properties were investigated. The results show that Mg/Al laminate achieves a sound welding quality by mechanical bonding and diffusion bonding. The obvious intermetallic compounds (β and γ) layer forms at Mg/Al interface, and its thickness increases to 8.3 μm as the extrusion temperature reaches 400 °C. High extrusion temperature promotes the dynamic recrystallization and grain growth of Mg and Al layers, while the dislocation density decreases. β/γ interface shows a coherent feature, while γ/Mg interface is semi-coherent with a locally ordered transition zone of 4.5 nm. The rich Mg and Cr layers are found at TiB₂/6061 interface, which is conducive to improving the bonding quality. When the extrusion temperature is 370 °C, the thickness of diffusion layer is around 5.0 μm, and the bonding strength reaches 18.68 MPa, resulting in the best comprehensive mechanical properties. This work provides a new direction for the development of Mg/Al laminate with excellent strength and ductility.