Interfacial ferrite band formation to suppress intergranular liquid copper penetration of solid steel

Intergranular liquid metal penetration, which is detrimental to the integrity of welded structures, has been widely investigated. Its mechanisms are now more clearly understood, but the suppression method is limited to optimizing processing parameters. In this paper, a metallurgical suppression technique by building an interfacial ferrite band to prevent intergranular liquid Cu penetration of solid steel was proposed. A ternary chemical potential prediction model was established and predicted that Si in liquid copper can accumulate at the interface and diffuse into steel during the interaction between molten Si-containing Cu and solid steel. This interaction can induce the formation of a ferrite band with a high resistance to intergranular liquid copper penetration of solid steel. A model for interfacial ferrite band formation based on Si diffusion during the interaction between solid steel and Si-containing molten copper was proposed and experimentally verified by welding-brazing copper to steel with Si-containing copper wire. The results indicated that long-range intergranular penetration was effectively suppressed, and harmless micropenetration appeared between the ferrite band and weld. The intergranular micropenetration mechanism is considered a grain boundary liquidation phenomenon induced by Si diffusion, differing from classical wetting theory.