Interfacial performance of stainless steel/carbon steel (SS/CS) laminated composite is crucial for further manufacturing and application. Here, we reported a new strategy for fabricating the SS/CS laminated composites that composed of heterogeneous lamella structure at the cladding interface zone, by employing liquid–solid bonding and subsequent hot rolling. Different rolling temperatures were applied for comparison of the formation of heterogeneous lamella structure and their influences on the mechanical properties of the cladding interface, and the mechanisms of enhanced interfacial shear strength and ductility by the heterogenous lamella structure were discussed. A metallurgical bonding interface with intensive elements diffusion was obtained by liquid–solid bonding method, and coarse equiaxed grains and a wider decarburized layer formed at the cladding interface zone. Under rolling temperature of 900 °C, the mechanical incompatibilities of cladding interface zone and lower temperature resulted in heterodeformation and inefficient driving force of recrystallization, resulting in a heterogenous lamella structure consisted of hardened austenite region, coarse-grained ferrite region and fine-grained pearlite and ferrite region at the cladding interface zone of SS/CS laminated composite, which obviously improved the interfacial shear strength and ductility of the SS/CS laminated composites due to back stress strengthening and hardening.
Stainless steel/carbon steel (SS/CS) laminated composites possess both excellent mechanical properties and low cost of CS and corrosion resistance of SS, which is a promising structural material for using in the field of chemical industry, petroleum and shipbuilding [, , , ]. The performance of the cladding interface of the SS/CS laminated composites that connecting the SS and CS is crucial for the further manufacturing and application [, , , ]. However, traditional bonding methods including explosion welding, diffusion bonding and hot rolling bonding result in limited diffusion distance of Cr, Ni and Fe elements through the cladding interface because of their lower diffusion coefficient under bonding conditions [, , , ]. Additionally, remarkable diffusion of C element due to superior diffusion coefficient leads to the formation of decarburizing layer and carburizing layer at the cladding interface zone during bonding process, which significantly decreases the interfacial bonding strength of the SS/CS laminated composites [, , ]. As a consequence, the interfacial shear strength of the SS/CS laminated composites fabricated by vacuum diffusion bonding decreases with increasing bonding temperature or bonding time . Apart from the diffusion, the stress and strain during hot rolling strongly affect the metal flow and microstructure evolution at the cladding interface zone, which also determines the interfacial bonding strength of the SS/CS laminated composites. Finer grains and oxides, decreased thickness of decarburizing and carburizing layers, increased diffusion distance of Fe, Cr and Ni elements are beneficial to improve the interfacial shear strength of the SS/CS laminated composites [12,15,16]. However, the differences between the diffusion coefficients of C, Fe, Cr and Ni elements restrict the improvement in the interfacial bonding strength of SS/CS laminated composites fabricated by solid–solid bonding method.
A new strategy of L-S bonding and subsequent hot rolling was proposed for fabricating SS/CS laminated composite, and the interfacial shear strength and extension of the L&R bonded SS/CS laminated composite reached the maximum of 407 MPa and 1.71 mm at rolled temperature of 900 °C.
A metallurgical bonding interface with intensive elements diffusion was obtained by L-S bonding method, and a heterogenous structure containing coarse-grained region nearing the cladding interface and fine-grained region formed in the Q235 CS under hot rolling temperature of 900 °C.