Interface nanocrystalline reinforcement mechanism of particle interlayer in pulsed current assisted rolling Mg/Al laminate

Abstract

Interface transition zone and the interface influence zone are critical factors in determining the interfacial bonding strength and ductility of heterogeneous metallic laminates. In this study, an innovative process—“cold spraying + pulsed current rolling”—is proposed for fabricating Mg/Al laminates, significantly enhancing both interface strength and ductility. Notably, the average interface shear strength achieved is three times that of conventional hot rolling, reaching 70.7 MPa, while the interface shear strain increases from 3.4 % to 28 %. The high-velocity impact of cold-sprayed aluminum particles on Mg and Al substrates forms a three-dimensional interface, effectively expanding the interfacial bonding area and refining the interfacial microstructure. The fine-grained coating structure produced by cold spraying acts as a primer, facilitating the formation of a nanocrystalline interface during pulsed current assisted rolling. The interface comprises an ultrafine nanocrystalline Al coating with grain sizes around 30 nm and β-phase nanotwins approximately 300 nm in scale, significantly enhancing the interfacial bonding strength. Together with the Mg and Al substrates, the nanocrystalline transition layer forms a layered gradient transitional structure that evolves into a 50-µm-wide interface-affected zone during deformation. This unique feature promotes strain delocalization, effectively mitigates strain concentration at the interface, and improves its fracture toughness. Additionally, the nanocrystalline interface increases the grain boundary area, promoting atomic diffusion and strengthening metallurgical bonding both between the coating and the substrate and within the coating itself. The “cold spraying + pulsed current rolling” process offers a straightforward approach to fabricating laminated nanostructured transition layers, demonstrating great potential in the interfacial design of heterogeneous materials.