Microstructure, mechanical properties and interface bonding mechanism of hot-rolled stainless steel clad plates at different rolling reduction ratios

Highlights: • Reduced delamination and intergranular cracks can enhance deformation coordination. • Ruptured Mn-Si oxide inclusions can promote interface diffusion and bonding. • Clad plates hot-rolled at 90% obtain the highest tensile ductility. • Martensite zone thickness is gradually decreased with the rolling reduction ratio. The microstructure, interfacial characteristics, shear behavior, tensile properties and fracture morphologies of stainless steel clad plates fabricated by vacuum hot rolling at different rolling reduction ratios of 20%, 40%, 70%, 90% and 93.75% are investigated using optical microscope (OM), ultra-depth microscope, scanning electron microscope (SEM), electron probe microanalysis (EPMA) and universal testing in detail. With the increasing rolling reduction ratio, the refinement degree of microstructure is increased, while the thicknesses of interface alloy element diffusion zones including the decarburized, carburized layers and martensite zone are decreased. Due to the different interface bonding status, the shear fracture of clad plate rolled at a low reduction ratio of 40% is located at interface, while clad plates with high reduction ratios of 70% and 90% fracture at the decarburized layers. Therefore, interface shear strength is sharply and then slightly increased. Moreover, the interface bonding strength, tensile strength and interface deformation coordination are increased, while fracture elongation is increased firstly and then decreased with the increasing rolling reduction ratio, which are attributed to the competing mechanisms of grain refinement, work hardening, interface strengthening and intergranular cracks of carburized layer. Overall, the interfacial bonding mechanism can be related to the Mn-Si oxide inclusions rupture, alloying elements diffusion, phase transition and severe plastic deformation at high rolling temperature.