Configuration evolution and bond-strengthening mechanism of multiscale interfaces in HPR Al/Mg/Al composite plates

In this study, we present the fabrication of Al/Mg/Al composite plates utilizing hard plate rolling (HPR) technology. Additionally, we have established a theoretical framework for the multiscale strengthening of the interfaces in HPR composite plates, which reveals synergistic effects between micron-scale wavy structures and nano-scale metallurgical bonding. Comparative experiments demonstrate that a 60 % reduction with a Mg/Al thickness ratio of 2:1 at 350 °C significantly enhances the thermal insulation effect of the hard plate, thereby promoting interfacial metallurgical bonding through mechanical interlocking structures. This results in a 91.7 % increase in the thickness of the diffusion layer. Electron backscatter diffraction (EBSD) characterization indicates that the interface of HPR composite plates exhibits a uniform grain distribution and a gradient transition in dislocation density. The thermal-force coupling field facilitates the formation of two types of intermetallic compounds (IMCs) during the rolling composite process. High resolution transmission electron microscopy (HRTEM) analysis reveals that the Al/β- Al₃Mg₂ and β- Al₃Mg₂/γ- Mg₁₇Al₁₂ phase boundaries create a common-lattice interface, while the Mg/γ- Mg₁₇Al₁₂ phase boundary accommodates the lattice mismatch through a semi-coherent interfacial dislocation network. Importantly, the groove-bump configuration at the β/γ phase interface illustrates the synergistic effects of geometrical interlocking and dislocation pinning, resulting in a 35.9 % increase in the ultimate tensile strength (UTS) of the HPR composite plate (223.5 MPa) compared to traditional rolled samples (164.3 MPa). Furthermore, the interfacial bonding strength is found to be 3.8 times that of the traditional rolled samples.