Interfacial strengthening of heterogeneous metals via geometric design in cold roll bonding

Driven by the increasing demands for high performance and multifunctionality, heterogeneous laminated metal composites often exhibit inclined interfacial geometries due to structural constraints. However, traditional cold roll bonding theory is limited to parallel interfaces and lacks quantitative laws governing geometry-dependent bonding quality, failing to guide the fabrication of complex geometric interfaces. This work reports a new method for enhancing bonding quality through proactive interface geometry design. Using a titanium-titanium/steel composite plate with inclined lateral bonding interfaces as a model system, we discovered that reducing the interface inclination angle acts as a “stress lever”, quantitatively translating macroscopic geometric parameters into local stress regulation at the interface: it significantly increases the normal compressive stress that promotes bonding while suppressing the tangential stress that causes instability. During room-temperature cold-roll bonding, the high normal compressive stress promotes the intimate contact of fresh metals at the atomic scale, achieving a firm metallurgical bond free of intermetallic compounds. This optimized stress state transforms the interfacial bonding mechanism from “slip-dominated limited bonding” at large inclinations to “high-stress-driven synergistic bonding” at small inclinations. Consequently, at a 50% reduction rate, the interfacial bonding strength surged from near-zero to 116.8 MPa. Based on this physical insight, we established a modified interfacial bonding strength model, building a quantitative relationship among interface geometry, the three-dimensional stress tensor, microstructural evolution, and interfacial bonding strength. The “material–geometry–stress” co-design principle established in this work provides a theoretical design framework for achieving precise manufacturing of high-performance heterogeneous material components.