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

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 Fe₂Ti. The FeTi/TiC + Fe₂Ti and FeTi/Fe₂Ti 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.