Optimized Second‐Pass Rolling of 9Ni/S30408 Clad Plates: Enhanced Interfacial Bonding, Mechanical Performance, and Deformation Mechanisms

9Ni steel/S30408 clad plates with excellent properties are prepared using second‐pass rolling composite process. The effects of first‐pass and second‐pass rolling temperature on the microstructure and mechanical properties of the matrix are explored, and the optimum rolling temperature is determined. It is found that interfacial bond strength of the 9Ni steel/S30408‐clad plate increases from 446.29 to 501.62 MPa as the first‐pass rolling temperature increases from 1050 to 1150 °C. However, the interfacial bond strength at second‐pass rolling temperature 800 °C is higher than that at 850 °C. When the temperatures of the first‐pass and the second‐pass rolling are 1150 and 800 °C, respectively, the comprehensive mechanical properties of the 9Ni steel/S30408 clad plate reache their optimum levels. The interfacial bond strength, tensile strength,and fracture elongation are 499.69, 795.33 MPa, and 25.79%, respectively. Additionally, the main deformation mechanisms of the two‐pass rolling bonding process are analyzed. For the 9Ni steel side, dynamic recrystallization occurs in the austenite fully recrystallized zone during first‐pass rolling to refine the grains, while second‐pass rolling in the austenite incomplete recrystallization zone produces defect‐rich deformation of austenite, preparing the microstructure for subsequent heat treatment. In contrast, the primary deformation mechanism for S30408 stainless steel is twinning.