Influence of continuous annealing on the interfacial compound evolution and mechanical behavior of hot-rolled titanium/steel composite plates

• A high-temperature short-time annealing process for hot-rolled Ti/steel composite plates with a pre-existing TiC layer at the interface has been developed and investigated. • The effects of the pre-existing TiC layer at the interface on the interdiffusion behavior of Fe, Ti, and C atoms, as well as the phase transformations within the interfacial layer, have been clarified. • Excessively high annealing temperatures promote the dissolution of the pre-existing TiC layer, resulting in the formation of Fe-Ti phases at the interface and a significant reduction in interfacial bonding strength. • The interfacial layer exhibits distinct failure modes depending on its composition. When composed of TiC, cracking occurs at the TiC/steel interface. In contrast, when composed of FeTi + Fe 2 Ti + TiC, cracking occurs at the FeTi/TiC + Fe 2 Ti interface. To investigate the effect of continuous annealing on the interfacial compound evolution and mechanical properties of hot-rolled TA1/St12 composite plates, the hot-rolled composites underwent heat treatments at 850 °C–950 °C for 10 min. The influence of the pre-existing TiC interlayer on interfacial reaction behavior and compound evolution was analyzed, revealing the interfacial bonding and failure mechanisms of the Ti/steel composites. Results show that at annealing temperatures ≤900 °C, the pre-existing TiC layer effectively suppressed the interdiffusion between Fe and Ti, thereby preventing the formation of Fe-Ti phases. The interfacial layer consisted of nanoscale and submicron-scale TiC. During deformation and failure, microcracks were prone to initiate at the nanoscale TiC/steel interface and subsequently propagate towards the nanoscale TiC/submicron-scale TiC interface. At 950 °C, the pre-existing TiC layer at the interface dissolved, and the interfacial compound layer evolved into a mixture of nanoscale TiC, FeTi, and Fe 2 Ti. The FeTi/TiC + Fe 2 Ti and FeTi/Fe 2 Ti interfaces became the primary crack propagation paths, severely degrading the bonding quality of the Ti/steel composite. After annealing at 850 °C, the ductility and deformation compatibility of the Ti/steel composite plate were significantly enhanced, resulting in optimal overall mechanical properties. The ultimate tensile strength, shear strength, and elongation were 286 MPa, 127 MPa, and 44 %, respectively.