Solid-State Diffusion and Intermetallic Phase Formation in Roll-Bonded Mg–Zn Composites with Kirigami-Patterned Inlay

ENG: Solid-state diffusion and intermetallic phase formation were examined in roll-bonded magnesium alloy–zinc (Mg–Zn) composites that contain a kirigami-patterned magnesium alloy (ZX10) inlay. The kirigami-patterned inlay was embedded between two zinc sheets and roll-bonded at 310°C. Subsequent heat treatments at 318°C and 328°C promoted interfacial diffusion as well as the formation of intermetallic phases. The kirigami geometry of the inlay was employed as a process-level tool to impose spatially inhomogeneous deformation during roll bonding. This caused localized stress concentrations, driving the controlled transformation of the initial pattern within the deformation zone. It also prevented the thin inlay from failing prematurely and ensured its controlled distribution along the sample. Inhomogeneous strain distribution introduced three-dimensional diffusion pathways that activated bonding and initiated phase transformation. Flexural testing revealed a significant increase in mechanical strength compared to values calculated using the rule of mixtures. The maximum strength observed was 100 MPa for samples heat-treated at 318°C. Microstructural analyses showed a progression from adhesive bonding (group A) to uniform intermetallic layers (group B) and complex, multiphase regions containing eutectic, dendritic, and porous fractions (group C). Energy-dispersive X-ray spectroscopy confirmed zinc diffusion into the magnesium solid solution, indicating the onset of solid-state alloying. The combined effects of plastic deformation, thermal activation, and the kirigami-patterned Zn inlay resulted in Mg–Zn composites with enhanced interfacial integrity and a tailored phase composition. These composites offer a promising pathway for advanced material compounds to be used in biomedical and mechanical applications.