Competitive mechanism between interfacial strengthening and TiC morphology in 45 carbon steel/TA2 clad pipes under wall reduction-controlled three-roll skew rolling

The fabrication of titanium/steel clad pipes requires a narrow process window, which necessitates balancing the contradiction between plastic deformation and the formation of high-temperature-induced brittle interfacial compounds, along with the complex coupling between reduction ratio and temperature parameters. This study systematically explores the competitive relationship between interfacial strengthening and TiC morphology in 45CS/TA2 clad pipes under wall reduction-controlled three-roll skew rolling at a relatively low temperature of 750 °C. Finite element simulations (Abaqus) reveal that an increased wall reduction rate intensifies thermal softening of the inner TA2 pipe. Mechanical testing and interfacial microstructure analysis demonstrate that the maximum interfacial shear strength (174 MPa) is achieved at a wall reduction rate of 23.5%, where a discontinuous diffusion reaction layer with minimal Kirkendall porosity is formed. At a higher reduction rate of 32.7%, the interfacial diffusion reaction layer evolves into a continuous structure, inducing the formation of a dense, continuous TiC layer (180-250 nm thick) and extensive pore proliferation, which results in a significant deterioration in interfacial strength. Grain structure analysis reveals that, at higher wall reduction rates, plastic deformation heat pro-motes abnormal grain coarsening, thereby counteracting the strain-induced grain refinement. In addition, the interfacial grain refinement zone exhibits a “discontinuous–continuous–discontinuous” transition, while TiC morphology evolves from discrete particles to a continuous layered structure as the reduction increases. This study elucidates the coupled mechanism between rolling-induced thermal energy and TiC phase transformation behavior, offering theoretical guidance for the process optimization of high-performance titanium/steel clad pipes.