Effect of corrugated -flat vacuum hot rolling and annealing on interface microstructure evolution and mechanical properties of TC4 / 316H composite plate

In this study, TC4/316H clad plate was prepared by corrugated-flat vacuum hot rolling, and the effects of post-rolling annealing on its microstructure and mechanical properties were studied by SEM, EBSD, TEM and EDS. The results show that the rolled composite plate exhibits the highest UTS (960.5 MPa) and shear strength (345.9 MPa), but the EL is only about 5.2 %. After annealing at 600 °C, the EL of the composite plate significantly increases to 17.4%, while the UTS and shear strength remain at 833.4 MPa and 239.6 MPa, respectively, with the shear strength meeting the requirement of GB/T 8547-2019 standard. This annealing temperature effectively eliminates rolling residual stress and greatly improves plasticity, while retaining qualified interface bonding strength and a high strength level, without forming a continuous brittle reaction layer at the interface. Recrystallization occurs preferentially in the near-interface region of the titanium side, and the degree of recrystallization reaches 12.5%. The shear fracture shows typical ductile fracture characteristics. After annealing at 700 °C, the interface properties of the composite plate deteriorate significantly, and the EL and shear strength decrease to 11.2 % and 145.3 MPa, respectively. It is confirmed by TEM that a continuous brittle reaction layer is formed at the interface, which is mainly composed of IMCs such as σ-FeCr, FeTi and Fe 2 Ti. The fracture mode is transformed into cleavage fracture along the brittle phase, which is the core reason for the significant decrease of interface performance.