Roll bonding and subsequent annealing behavior of Ti–6Al–4V/9Cr18MoV composite plates with pure Ni as the interlayer

Dissimilar roll bonding of titanium and its alloys to high strength steels are attracting more attention due to the integrated merits from both metals, maintaining high strength while exhibiting substantial weight-reduction and anti-corrosion properties. However, high-carbon (> 0.45 wt.%) martensitic steels have barely been utilized for bonding with titanium, due to the extremely high tendency of forming brittle TiC compound. Here, we present the roll bonding of TC4 and 9Cr18MoV with pure nickel as the interlayer, followed by controlled annealing at temperatures of 850, 900, 950 and 1000 °C. The interfacial microstructural evolution and mechanical properties were focused and systematically analyzed. It was found that during the hot rolling stage, the Ni interlayer effectively hinders the diffusion of Fe into the titanium side through a physical barrier effect. During the annealing stage, intermetallic compounds (IMCs) such as TiNi were formed, along with the formation of intermittent TiC compound. More importantly, the thickness of TiC ranges from 0.9± 0.14 to 2.22± 0.27 μm which is attributed to the low diffusivity of carbon in Ni and thus did not deteriorate the bonding significantly. Our study clarifies the functional role of the Ni interlayer in regulating interfacial reactions with bonding Ti and Fe, as well as the formation mechanism and evolution trends of the TiC phase at the interface, providing theoretical guidance and process insights for the interfacial strengthening and toughening design of titanium/high-carbon steel composite materials.