Bonding process and mechanisms of interface evolution of stainless steel clad plates fabricated by cyclic phase transformation heat treatment

Stainless steel clad plates have been largely used in engineering applications because of their excellent mechanical properties. Thus, there are many kinds of composite processes to prepare stainless steel clad plates. In general, the temperature is one of the most important parameters in the bonding processes, which is studied as a constant value. In this work, a novel bonding process using cyclic phase transformation heat treatment was subjected to manufacture stainless steel clad plates. The results reveal that stainless steel clad plates are successfully bonded. The joining process of the composite interface can be divided into three stages: the appearance of long interface voids, the shrinkage of long interface voids, and the formation of the continuous austenite phase. Microstructural analyses suggest that recrystallization and element diffusion occur during the bonding. Compared with isothermal heat treatment, it is obvious that this process can avoid ferrite grain coarsening. Moreover, the joining efficiency can be improved significantly by accelerating the transformation of the ferrite to the austenite at the interface. The shear test demonstrates that the shear strength of stainless steel clad plates after cyclic phase transformation heat treatment is larger than that of isothermal heat treatment in the same bonding time. The dimples on the shear fracture surface also dramatically increase.