Interfacial microstructural evolution and mechanical properties of Al/steel/Al composite sheets prepared by "cold spraying + hot pressing + hot rolling"

Al/steel/Al composite sheets were fabricated using a multiprocess synergistic optimisation approach combining cold spraying, hot pressing and hot rolling. A systematic investigation was conducted on the bonding properties, interfacial microstructural evolution, and mechanical properties of the sheets. The results demonstrated that the hot pressing-hot rolling treatment not only reduced the porosity of the aluminium layer to 0.08 %, resulting in the densification of the sheets, but also significantly enhanced their overall tensile strength and interfacial bonding performance. After hot rolling with 58 % reduction, the tensile strength of the sheet reached 353.8 MPa, which is three times that of the cold-sprayed Al/steel/Al composite sheet, while the interfacial shear strength exceeded 100 MPa. Interfacial analysis revealed the formation of a unique bonding structure at the interface. Mechanical anchoring and diffusion bonding were observed at the Al 2 O 3 /steel and Al/steel interfaces, respectively. This synergistic effect significantly improved the interfacial bonding quality of the sheet. Additionally, post-annealing interfacial analysis indicated favourable interdiffusion characteristics at the Al/steel interface. Digital image correlation was employed to monitor the tensile process of the hot-rolled Al/steel/Al composite sheets. Their strain distribution evolution was systematically analysed to elucidate the effect of the interfacial bonding performance and matrix strength optimisation on the deformation behaviour.