Role of interfacial oxygen level in governing bonding mechanisms and mechanical properties of Ti/Mg laminates

This study investigates the influence of interfacial oxygen engineering on the microstructural evolution and mechanical performance of hot-roll-bonded Ti/AZ91 laminated composites. Four controlled oxygen conditions were established prior to bonding to systematically tailor the interfacial chemistry while maintaining identical rolling parameters. Increasing oxygen content induced a progressive transition from direct metallic bonding with discrete oxide particles to the formation of a continuous oxygen-rich interlayer. At an intermediate oxygen level, a hybrid amorphous–nanocrystalline interfacial structure developed, enhancing interfacial integrity and load transfer. Accordingly, the medium-oxygen (M-O) laminate exhibited the highest tensile–shear strength of 91 MPa, together with improved tensile ductility and more cooperative deformation behavior. In contrast, excessive oxidation promoted the formation of a continuous brittle interlayer, resulting in a pronounced deterioration in mechanical performance. Fractographic and phase analyses further revealed a transition from predominantly cohesive fracture to oxide-mediated adhesive failure with increasing oxygen content. These findings demonstrate that interfacial oxygen engineering provides an effective strategy for tailoring bonding mechanisms, interfacial structure, and mechanical performance in reactive multi-material systems.